US2750576A - Vehicle actuated traffic signal apparatus - Google Patents

Description

June 12, 1956 w. H. BEAUBIEN VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUS Filed Aug. 2e, 1952 5 Sheets-Sheet l Inventor: William l-l. Beauben,

His Attoney June 12, 1956 w. H. BEAUBIEN 2,750,576

VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUS Filed Aug. 26. 1952 3 Sheets-Sheetv 2 lnverwtorf n William HBeaubien,

by H s Ati-.ovm ey,

June l2, 1956 w. H. BEAUBlEN VEHICLE ACTUATED TRAFFIC SIGNAL APPARATUS 5 Sheets-Sheet 3 Filed Aug. 26, 1952 www Inventor. William Heaubien,

His Attorrl ey.

United States Patent O VEHICLE AC'.TIJAJIEDV TRAFFIC SIGNAL APPARATUS William H; Beaubien, Lynn, Mass., assigner to General Electric Company, a corporationl of New York Application August 26, 1952Serial No. 306,472

49 Claims. (ci. 34a- 35)- Myy invention relates to traiic signal control systems, and' more particularly to vehicle actuated tratic signal control systems and apparatus therefor.

Vehicle actuated tratlic signal control systems. are distinguished. from xed time, or pre-timed, systems'l in that avelcle actuated system initiates alternations of or controls the duration of the right ofway grantedby the traic signals tointersecting trafc lanes in direct: response. tothe presence of vehicles on. one or more of the intersecting lanes. Vehicle` actuated systems are fully actuated when subject. to actuation in response tovehicle detectors located in all of the intersecting traiic lanes,` and semiactuated when subject to actuation only in response. to vehicle detectors located in less than all of the intersecting lanes. Fully. actuated traiiic signal control systems may operate so that the right of' way remains upon the trac lane to which it was last called, known as floating operation, or the right of way may alwaysl revert to a selected one of the traffic lanes, known as reverting operation. Alternatively, a fully actuated traiiic signal control system may be operated in the absence of traftc in a normally cyclic standby manner by providing continuous automatic alternation ofthe right-of way by means ot' a timer, traic actuations being operable either to curtailor to extend the right of way intervals of the normally cyclic standby operation. it willbe appreciatedof course that a semi-actuated control system may operate normally cyclically or as a reverting type, the right of way reverting to the lane in which no detectors are provided, but is not operable as a floating system.

It will of course be understood that pre-timed traic signal controllers mustbe preadjusted to careV for one particular preselected traiiic condition. For example, one of twof intersecting streets may be regarded as the major street and accorded more than halfthe cycle time; At some' intersections, however, the relative importance (in traii'icl density) of two intersecting streets maycliange at' different times` of the day. Vehicle actuated systems generally adapt themselves automatically to such changing conditions with, of course, various degrees of reinement.

It hasbeen recognizedheretofore that vehicle actuated traiiic signal control systems of the fully actuated type should be provided with both minimum and maximum right of way intervals on all intersecting lanes, and that semi-actuated traic signal control systems should .be provided With minimum and maximum right of way intervals upon the actuated lane and with a minimum interval on the non-actuated lane. A minimumintervalisas its name implies, the least interval accorded to anylaneonce the green light has been accorded to it. A maximum right ofway interval, as will appear, is necessary to prevent right of way extension intervals demanded by` cars from holding a right of` way continuously. Without more, however, such systems becomein eiect xed timesystems in theevent that trahie on all actuated lanesisvery heavy because the predetermined maximum right of way inter- 2,750,576 Patented June 12, 1956 rice vals are repeatedly accorded to each street. Under such conditions', therefore, such elementaryA actuated systems fail in. their function of recognizing and operating in accordance with relative trafc density on the intersecting lanes.

It is an object of my invention to provide a vehicle actuated traic signal control system of the fully actuated type which may be readily adjusted for reverting-floating or normally cyclic standby operation, and which in. all sucht modes of operation functions automatically toi determine rightfof way intervals on intersecting traic lanes, which intervals are continuously proportioned in accordance with the relative tratc density on the lanes, as long as traic actuations are suiiiciently closely spaced to preelude normally cyclic standby operation when such: operation is provided.

ltI is still another object of my invention to provide a new traffic actuated signal control apparatus wherein the limiting right of way interval available to any of a plurality of intersecting traiiic lanes is variable in response to relative traic density on the lanes.

A particular object of the invention is to provide, in al semi-actuated or fully actuated traic signalcontrol apparatus, means for extending the limiting right of way interval available on any actuated lane in response to vehiclesapproaching on that lane when grantedv the'right of way.

Another object of the inventionis to provide, in'a fully actuated traffic signal control apparatus, rneansfor reducing the limiting right of way interval available on any lane in response to traffic approaching on the other lane.

it i'sstill another object of my invention to provide, in a semi-actuated traic signal control system, means responsive to vehicles approaching on a stopped actuated traffic lane for reducingthe minimum right of wayinterval normally granted to the non-actuated lane.

A further object of'the invention is the provisionin a fully actuated traiic signal controller, of means for increasing the limiting right of way interval on a moving lane in response t-o traffic approaching on the moving'lane, decreasing said interval in response to traffic approaching on the stoppedlane, and still'retaining an ultimatelimiting time when right of way is automatically removed.

A more particular object of the invention is to provide in a vehicle actuated signalling apparatus, means for extending the limiting right of way interval available on any traic lane in accordance with vehicles stored on the lane between the detector and the light prior to the time such right of way was granted.

In a principal aspect my invention provides a` vehicle actuated timer which is set into operation,-normally, by the trst'car or other vehicle approachingA the intersection against the red light. As will hereinafter appear, the timer may also be set in operation automatically, as by automatic recall in reverting operation. Vehicles approachingona lane having the green light demandV and obtain vincremental extensions of the right ofy way time. To preclude permanent retention of the right of'way by one laneY when even a single car is waiting` on the other lane, a limit, called an extension limit interval, is imposed beyond which the right of way time cannotY be extended. To-better follow traffic conditions this extensiony limiting time is variable in increments both inv accordance with cars approaching on and cars approachproaching against the right of way as in a oating system. My limiting interval, however, has no arbitrarily predetermined duration but is varied incrementally, both by increase and by decrease, in accordance with exlstmg traffic conditions. Even the ultimate limiting time which is imposed despite continued efforts to increase the limit, is of no fixed predetermined length, but is measured by the density of traic approaching on all intersecting lanes.

In carrying out my invention in one form, I utilize a rotatable signal sequence drum which is provided with a plurality of switching positions and which is turned from one position to another by means of an electric motor. In its various switching positions the sequence drum actuates switches to control the red, amber and green lights in a traic signal device located at the intersection of one or more streets (hereinafter referred to as traffic lanes). The motor driving the sequence drum is controlled by suitable vehicle detectors (i. e., car operated switches) positioned in or near one or more of the intersecting traic lanes, this control of the driving motor being modified, however, by a plurality of timing devices which introduce predetermined time intervals and time interval limits in accordance with traffic conditions as indicated by the repeated actuation or non-actuation of the detector switches by vehicles approaching the intersection. The detectors are normally positioned an appreciable distance from the intersection (for example 100 to 300 feet), so that vehicles crossing a detector on a lane having the right of way require a clearance time, and vehicles approaching against a red light are stored between the light and the detector.

The sequence drum is provided with certain standby or rest positions in each of which the right of way is granted to a different one of the intersecting trac lanes, the number of stand-by or rest positions on the drum corresponding to the number of lanes to which the right of way is granted in a complete cycle of operation. It will be appreciated that in a semi-actuated apparatus only one such position is properly called a stand-by or rest position and the intermediate right of way positions on the drum are more properly called dwell positions. In floating or reverting operation the signal sequence drum normally remains at rest in one of its stand-by positions until it is moved to grant the right of way to another traffic lane in response to actuations of the detector on that other lane. In automatic recall, or normally cyclic, operation, of course, the drum may also be moved Afrom the rest position or positions in response to an automatic call circuit controlled by a manually operated recall switch.

During automatic actuation under the control of the car actuated detector switches in the intersecting street (i. e., except in stand-by operation), the duration of the right of way granted to any actuated traffic lane is made up of an initial time interval determined by the controller in accordance with the number of cars passing over and actuating the detector switch in the stopped street prior to the transfer of the right of way to that street, and in addition one or more vehicle extension intervals which may be added to the initial interval in overlapping time relation in response to actuations of the detector switch by cars approaching the intersection on a lane having the right of way. It is a feature of my fully actuated control apparatus that in the event no additional car approaches and actuates the detector switch on a street after the right of way has been granted to that street, no extension time interval is granted to that street, provided of course that the right of way on the intersecting street is demanded by approaching cars before the end of such initial interval.

The timers for determining the period of time that each street has the right of way, in accordance with trac conditions as evidenced by repeated actuation or nonactuation of the car detector switches, include a timerA for each street for determining the initial time interval in accordance with the number of cars approaching wherr the particular street does not have the right of way, and for adding to these initial intervals extension intervals: determined by the additional approaching cars after the street is given the right of way by the green light.

I also provide an additional timer, transferred by the sequence drum from one street to the other, for imposing a limiting time on the car extension intervals and moreover for transferring the right of way substantially instantaneously if cars are waiting on the stopped street and cease to approach or are widely spaced on the right of way street. It is a feature of my invention as applied to full actuation that the extension limit time interval introduced by this additional timer is progressively reduced in response to cars approaching on the stopped street and progressively increased in response to cars approaching on the right of way street. In a semi-actuated apparatus, I utilize this additional extension limit timer to determine a minimum right of way interval on the non-actuated street.

In a fully actuated controller, l provide means whereby cars approaching on a stopped lane and thus predetermining a subsequent initial right of way interval on that lane, also increase the maximum extension interval ap plicable to such subsequent right of way interval. The extension limit timer, however, inherently includes anl ultimate timing characteristic beyond which the moving lane cannot hold the right of way.

Itmay be further briefly noted that my controller is characterized also in that vehicle extension intervals demanded by cars approaching on the moving lane are not cumulative but are overlapping, each new vehicle extension interval cancelling the remaining portion of the previous extension interval, so that no more than one complete vehicle extension interval is stored in the timer at any one time. This characteristic corresponds to traffic conditions, in that the vehicle interval which is operative is that demanded by the last car to cross the detector, all other significant cars being ahead of this car.

It is a further feature of my fully actuated controller that in the event cars cease to actuate the detector on the moving lane or arrive at intervals greater than the vehicle extension intervals, a short delay in transfer of the right of way to the other lane is imposed, so that a car approaching on the moving lane has a time advantage or preference over a car approaching on the stopped lane.

My invention itself will be more fully understood and its various objects and advantages further appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawings, in which Fig. 1 is a schematic circuit diagram of a fully actuated traic signal control system embodying my invention; Figs. 2 to 5 inclusive are simplified elementary circuit diagrams of certain significant timing circuits included in Fig. l, these Figs. 2 to 5 being drawn for only one phase of the operation for the purpose of simplification; and Fig. 6 is a schematic circuit diagram of a semi-actuated trafiic signal control system embodying my invention.

Fully actuated apparatus Referring now to the drawing, and more particularly to Fig. 1, I have there illustrated a vehicle actuated trai-lic signal control apparatus suitable for application to a pair of intersecting traic lanes. The apparatus includes a pair of vehicle detectors, or vehicle responsive switches, 1 and 2 adapted to be positioned beneath or adjacent the intersecting traic lanes. The detector 1 is associated with one lane, A, and the detector 2 is associated with the other lane, B, and each detector switch is closed momentarily whenever a vehicle approaching on thev associated lane passes a predetermined point spaced back `from fthe intersection. It will, of course,`be understood that where trac proceeds in opposite-.directions on each lane, or street, a second .detector switch would be in parallel circuit relation with each detector switch l1 and `2. There is provided also a suitable Signal device 3of the type comprising a red,amber and :green indicating light for each intersecting traiiic lane. interposed 4between the detectors 1, 2 and the signal device 3, Tprovide a controller operable in response to actuations of the detectors to control the lights. This controller includes a rotatable signal sequence drum 4 having switch operating cams and sixteen discrete switchingpositions, asindicated schematically inthe drawing, the drum'being advanced by a motor 5. The signal vdrum has associated therewith six cam operated switches, RA, AA, GA, RYB, .AB, GB, connected to control the lights in the .signal device .3. The drum also controls a Vplurality of other -cam operated switches, C1 to C12 inclusive, operable in conjunction with the various'timing circuits, as will be 'hereinafter explained.

In addition, the controller includes five electronic timers, .each timer including a grid-controlled electron discharge tube, and the .tubes being shown as three element vacuum tubes, T-l, T-Z, T43, T-4 and T45. The timing tube T-l is in the initial interval and vehicle extension interval timer for the lane AA, and the timing tube T-2 is in the corresponding timer for the lane B. yThe timing tube T-S is in the extensionlimit vand ltransfer timer, which timer is operable in conjunction with both lanes, while the tube T-4 is in an extension limit increase timer operable in conjunction with both lanes. The tube'T-S is in an amber interval timer also operable in conjunction with both lanes. All 'the timing tubes nare arranged to be normally conductive and are provided With grid vcapacitors which are adapted to maintain the .associated tube non-conductive when negatively charged. Each grid capacitor is provided with one or more discharge resistors through which any negative charge accumulated on the capacitor is permitted at times to de- Cay, thereby to determine certain delay intervals rbefore .tube conduction. The extension limit .and amber timing tubes T-3 and T-S, respectively, are arranged when conductive to effect Vclosure of the drum motor energizing circuit, therebyto move the drum through a singleposition. The extension limit timing tube T-3 is vprovided with aplurality of grid capacitor discharge resistors, and these various discharge resistors are controlled in their connection to the timing capacitor 'C-3 by'means of the extension limitincrease 'timing tube T-4 and one or the other of the initial and vehicle extension interval timing tubes T41, T-2.

More specifically, the timing tubes T-1 to T-5, inclusive, are provided with grid capacitors C-1, C-Z, C-3, C-'4 and C-5, respectively, and`witl1 anode or .plate relays R-l, `R2, R-3, R-4 and R-S, respectively. The plate relays of the timing tubes T-3 and T-S are connected to controlthe energizing vcircuits for the program drum motor S, while the plate relays of the timing tubes T-l, T-Z and T-4 are connected to control various discharge circuitsfor the extension limit timing capacitor C3.

The vehicle detectors 1 and 2 are connected to control :detector relays D-l and D-2, which are connected to beheld closed'for a predetermined fixed impulse interval upon each vehicle detection. The impulse timing of the detector relays is accomplished by a pair of detector timing relays DT-l and DTF-2, respectively. In addition, vthere are provided a number of transfer relays controlled 'by various contacts on the sequence drum. A transfer Arelay vTR-l is connected to control the circuit -of the capacitor "C--1 for the timing tube T-1, and a similar transfer relay TR-Z is connected to control the circuit of .the capacitor C-2 for the timing tube T-Z. A .pair of .transfer relays TR-S and 'IR-4 are connected to control the cathode circuits of the extension limit timing tbe T-3 and to transfer the connections of these cir- .cuits in .theinoperation in .conjunction with the alternate operating .phases A Atransfer .relay "FR-5 zis ;provided to transfer @the connections of the extension limit `increase and amber interval timing Atubes T4 and T11-5, frespectively, .in .their f different y,phases .of operation, and ,-a transfer .relay `'1`.R-6 is v.provided to transfer connections -of the .chargingcircuits for the timing capacitors C-i `and .C-.2 as Ythe right of way is:transferredfrom lane-to lane.

Fully actuated ope'raton-Generdl The interaction of the various timers andrelays in :controlling the ladvance of the sequence-drum 4, `and additional functions .of the -timers and relays, will be most readily .understood by proceeding now to .describe the -operation of lthe device :under-typical y.conditions of traic actuation. ln describing the oper-ation, the .advance of the drum =wil1 be traced through onlyfav single .halfcycle, i. -e., from onerest position to rtheother, the other half cycle being obviously effected in .an .entirely -similanman- ..ner. For the purpose `of clarity, emphasis will y'first .be placed upon the more fundamentalaspects of .the drum advance, certain improvement features and rrenements being separately Adiscussedin more detail after a single lhalfcycle of-.operation. has been traced.

Theoperation `williirst be described in conjunction Vwith Fig, .1, showingacomplete.fullyactuated apparatus. Certain Vof the-significant tubetimingcircuits-of Eig. 1 areex- .tracted `in 4elementary 4diagrammatic .form at Figs. V2-5., zinclusive.

.Referring now to lFig. l, .the signal sequence drum 44 is, .as described, .associated with a pluralityof vcam switches, sixof which .controlthe traicsignal device Sand there- .maining of=which `control .the various transfer :relays `and other sequencing circuits .in `the controller. The drum is .providedwith sixteen switching positions .representing .one complete `cycle .of operation, positions 3 :and .1-1 .be- :ing the rest positions from which thedrum .w`ill.not ,ad- Vance without further .traflic actuation or .automatic call. .For-simplicity of illustration, .the cam switches anddrum lhave-.been-shown (LFgS. l and 6') ydiagrammatically with .allswitches shown open. The horizontal broken Alines (numbered) represent .drum positions, land the solid vertical lines -on vthe drum vindicate those drum positions in which the cam -switch vertically 7aligned `with each such -solid'lineisclosed In position 3 the switch .GA is fclosed, so fthat.lane.A .has the right of way, as ndicatedon theswitch sequence diagram shown in conjunction with the diagrammatic representation-'of the drum, while-imposition yf1.1 1the-switch -GB is closed, so-that lane -B has-the rightof Way. .For-.the ,purpose-of illustration, .the controller `will -be considered .inth'at mode of operation in Awhich the .right vof 'way-relmains upon the street to which it was last called. This -is the `mode of operation previously referred to as floatin-g operation, `and is-carried outin v.the subject controller by leaving the recall switches R1and R2 `both open. In ,.general, it may be'observed that'if .the sequence drumvis advanced-from eitherposition 3 or position 11 bya vehicle actuation, the various -timers automatically yadvance the drum through-the intermediate positions :to fthe -inex-.t rest position, `where the drum .then remains until l.again advanced by traffic actuation, `the time 'intervals during "which Athe drum dwells'on each -of the intermediate positi ons Vbeing determined by various .timers i in vthe apparatus.

`Itmaynow be noted that all relays-andrelay.contacts lare shown in vtlieir-deenergized positions, andsuch positionsare referred to hereinafter as dropped-.oufpositions. lt willbe understood that when any .relay is energized its contacts (shown along a single vertical '.broken line) are all moved simultaneously to their kupper .positions, and the relay is then said to be picked-up.

iF ig. 1.-Fl0atng operation- Transfer lane .to .lane d? Let it now be assumed that the sequence drum .is in position '3, indicating Athatlane A was 'the street to which the right of way was last called, and let it be further assumed that no traflic actuations have taken place for a considerable length of time, so that the entire apparatus is in a steady state or stand-by condition. In this condition, the lane A initial interval and vehicle extension interval timing tube T-l and the corresponding lane B timing tube T-Z are both conductive, since their grid capacitors C-1 and C-2, respectively, are discharged to the point where grid-to-cathode voltage is substantially zero. The relays R-1 and R-2 are therefore picked up and the relay contacts are moved into the opposite positions from the positions shown at Fig. 1. The maximum timing capacitor C-3, however, is charged to maximum voltage, and the tube T-3 is not conductive, both because of such charge and because its cathode circuit is open at the recall switch Rz and at a contact 43a of the plate relay R-2. The full charge on capacitor C-3 exists because a slow rate charging circuit is completed from a voltage divider 7 and a potentiometer 8 (as a source) through contacts 10 and 10a of relay TR-3, a cathode resistor 9, and the grid-tocathode space of the tube T-3. (A similar potentiometer 8a is provided for the opposite operating condition-i. e., drum position 11.)

In this drum position V3 also, the cam switches C1, C3, Cs, and Cs are closed, as indicated upon the diagrammatic representation of the sequence drum. Through the cam switch C1 the transfer relay TR-1 is picked up and its contacts 11 and 11b are positioned to connect a discharge resistor 12 across the timing capacitor C-1. Through the cam switch Ca the anodes of the timing tubes T-1 and T-Z are connected to one side L-1 of an alternating current supply transformer T, the other side of which is represented by L-2 and the center of which is grounded. Through the cam switch Cs the transfer relay TR-S is picked up, so that its three selector contacts 13, 14 and 15 are vproperly positioned for operation with lane A having the right of way. Through the cam switch Cs a high resistance discharge resistor 16 is connected in parallel circuit relation with the timing capacitor C-3 of the extension limit timing tube T-3. However, the foregoing slow rate charging circuit referred to in the preceding paragraph maintains capacitor C-S charged. It will be noted that no discharge circuit is completed for the timing capacitor C-2 of the lane B timing tube T-2. In addition, the detector relays D-l and D-Z and the detector timing relays DT-l and DT-Z are dropped out, while the detector switches 1 and 2 are open.

Impulse interval-1f now a vehicle actuation is received upon lane A which has the right of way, the detector switch 1 is closed momentarily while the vehicle passes over it, thereby to complete an energizing circuit for the detector relay D-l through normally closed contacts 17, 17a of the detector timing relay DT-1. (Similar contacts 18, 18a, 18h are provided on relay DT-Z for lane B detection.) When the detector relay D-1 picks up, it opens its normally closed contacts 19, 19a and closes its normally open contacts 19, 19b. (A transfer contact 19C on detector relay D-Z corresponds for lane B detection to contact 19 on D-l.) Closure ofthe contacts 19, 19bl completes an energizing circuit from the supply conductor L-1 through a rectilier R and a capacitor 20 to the energizing coil of the detector timing relay DT-. Thus, unidirectional current is supplied to pick up and hold energized the timing relay DT-l only for an interval suicient to charge the capacitor Ztl. A resistor 20a shunting the capacitor 20 serves to determine the impulse interval, but so limits current that the relay DT-l will not hold closed after the capacitor is charged. Energization of the relay DT-1 completes a holding circuit for the detector relay D-1 through the normally open contacts 17, 1711 of the relay DT-l. ln this manner the detector relay D-1 is held energized for a predetermined impulse time determined by the charging time of the capacitor 20, regardless of the speed of the vehicle. When the timing relay DT-Vl drops out, the holding circuit for the detector relay D-1 is broken and the relay D-1 drops out. In its drop-out, the relay D-1 again closes its normally closed contacts 19, 19a thereby to shunt and discharge the timing capacitor 20. The relay DT-2 operates in like manner for lane B with a capacitor 21 and resistor 21a.

Extension intervals.-Energization of the detector relay D-1 also opens its normally closed contacts 22, 22a, thereby to interrupt the cathode circuit for the timing tube T-1 and render the tube non-conductive, and at the same time closes its normally open contactsy 22, 22h, thereby to complete a charging circuit for the grid capacitor C-1 of the tube. This charging circuit may be followed from the power supply line L-Z through a resistor 23, the capacitor C-1, the grid-to-cathode space in the discharge tube T-l, the contacts 22, 22b, and the normally open contacts 24, 24b on the transfer relay T-1 to the slider 25 of a potentiometer 26a, 26b, 26C, 26d. Through this circuit a predetermined charge is placed upon the capacitor C-1 which renders the grid of the timing tube T -1 negative. Thus, when the detector relay DD-l drops out, the timing tube T-l remains n0nconductive and relay R-l is dropped out for a time sufcient to permit the negative charge upon the capacitor C-1 to discharge through the resistor 12. This nonconductive interval of the timing tube T-1 represents a vehicle extension interval in the controller during which transfer of the green light away from lane A cannot be effected. Such vehicle extension interval must be suficient to permit a vehicle moving at some predetermined normal speed to clear the light. Of course, if no car has approached on the stopped lane B, there would be no tendency to transfer the right of way to lane B.

If, however, a car had approached on the stopped lane B at any time beginning slightly before the approach of the car on the moving lane A (thereby to drop out relay R-Z as will be later explained), the non-conductivity of the timing tube T-1 and consequent drop-out of its plate relay R-l would act to prevent the transfer until the tube T-1 again became conductive.

This drop-out of the lane A relay R-1 for a vehicle extension interval insures maintenance of the right of way on lane A because it prevents rapid discharge of the extension limit timing capacitor C-3. Referring to the grid circuit of the extension limit timing tube T-3, it will be observed that three discharge resistors 16, 27 and 28 are provided. The capacitor C-S cannot discharge through the resistor 27 even though a normally open contact 29 on the detector relay D-l is momentarily picked up, because the detector relay D-2 is dropped out (to open its contact 30) and contacts 31, 31b on the transfer relay TR-3 are open. The capacitor C-3 is not discharging through the resistor 16 because the charge on C-3 is being maintained through resistor 9 as previously described. The resistor 28 is a relatively small transfer resistor through which the capacitor C-.3, when connected, may dischargein approximately one second. This resistor 23, by thus rapidly discharging the capacitor C-3, effects a substantially immediate transfer of the right of way by rendering the timing tube T-S conductive, as will be pointed out hereinafter. However, because of the drop-ont of the plate relay R-l for lane A, the capacitor C-3 cannot discharge through resistor 28 at least until the relay R-l (which is measuring a vehicle extension interval) is again picked up. This is because the discharge circuit for capacitor C-3 through the resistor 28 must be followed from the grid of the tube T-3, through the drum contact Cs, normally open contacts 32, 32h on the plate relay R-4 (now closed because the tube T-4 is conducting), a normally open contact 33 on the lane A transfer relay TR-l (now closed through drum contact C1), and normally open contacts 34, 34b on the lane A plate relay R-l. The contacts 34, 34h, now being held open for the duration of a vehicle extension interval, on the transfer resistor 28 cannot be con- 'andere nected across 'the capacitor lC-'3 even if a car does approach on the stopped lane B (which drops outplate relay 'R2 thereby to close the cathode circuit of tube T-3 as will appear hereinafter).

Initial interval measurement- If now a car approaches on the stopped lane B (i. e., against a red light) during the vehicle extension interval previously described, the detector relay D-2 is momentarily picked up. This momentary pick-up is through detector 2 and contacts 18, 18a of relay DT-Z, and is timed by capacitor 21, in the same manner previously describedfor a lane A actuation. When relay D-2 picks up, it opens the cathode circuit of the timing tube T-2 at its contacts 35, 35a and completes a charging circuit for the lane B timing capacitor C-2 4by closure of its contacts 35, 35b. This charging circuit may be followed from a point 36 on a potentiometer 37a, 37b, 37e, 37d, through contacts 38, 38a on relay r1R--6, the capacitor C-2, the grid-to-cathode space in 'the discharge tube T-2, the contacts 35, 35b on the detector relay D-2, normally closed contacts 39, 39a on the transfer relay TR-Z, and a variable resistor 40. A similar resistor 40a is provided in the like charging circuit of capacitor C-1. This charging circuit is closed only momentarily by the detector relay D-2 so that a small predetermined impulse or increment of charge is placed upon the capacitor C-2, thereby to render the grid of the discharge tube T-2 negative. Additional lane B detector actuations by cars approaching the red light add further increments of charge to the capacitor C-2, thereby predetermining a longer discharge time for the capacitor when a discharge circuit is later completed through its associated discharge resistor 41. As will hereinafter appear, this incremental charging of the capacitor C-2 by cars approaching on the stopped lane predetermines an initial right of way interval for lane B when the right of way is transferred tothat lane.

Also, the charging of this capacitor C-2 by the approach of the rst vehicle on the stopped lane B renders the tube T-2 non-conductive, thereby to drop out the lane B plate relay R2. When the relay R-2 drops out, it closes its normally closed contacts 42, 42a and 43, 43a. These contacts 42, 42a prepare a discharge circuit for the eX- tension limit capacitor C-3 through the rapid transfer resistor 28. This discharge circuit, however, remains incomplete so long as cars approaching the moving lane A are retaining the relay R-l dropped out 'to time vehicle extension intervals, thus maintaining the contacts 34, l34b open.

The contacts 43, 43a complete connection of the cathode of tube T-3 to the supply line L-2. This connection shunts resistor 9 and potentiometer 8 and thus initiates discharge of capacitor C-3 through the extension limit resistor 16, thereby to begin the timing of an extension limit interval for the moving lane A.

Transfer.-With cars thus waiting on the stopped 'lane B as described, it may now be observed that if a sufficiently long break in the traffic approaching on the moving lane A occurs so that the vehicle .extension interval demanded by the last preceding car expires without another car approaching, the timing tube T-1 again becomes conductive thereby'to energize its plate relay R-1 and close the contacts 34, 34h. This prepares a discharge circuit for the capacitor C-'3 through the rapid transfer resistor 28, the contacts 42, 42a on relay R-2, the contacts 34, 341; on relay YR-l, the contact 33 on relay'TR-l, the contacts '32, 3'2b on relay R-4, and the drum contact Ca.v

It may now be noted that the foregoing discharge circuit for the rapid transfer resistor 28 is delayed in completion when, as described, vehicle extensions have been demanded by cars on thegreen lane A. Whenever alane A extension interval expires so that the plate relay R-1 picks up, as described, this relay not only recloses contacts 34, 34h, but also closes its contacts 44, 4411 toplace a pair of resistors 45 and 46 in parallel in .the charging circuit of capacitor C-4. VThe resulting change in grid voltage ontube T-4 causes thattube Vto shut off and relay R-4 to drop out for a short delayinterval whenever the relay R-`1 picks up. The discharge vcircuit -for. 4C-S through resistor 28 is completed when T-4againconducts. This delay insures full discharge of capacitor C-l to la predetermined voltage prior to transferfof theright'of way to lane B so that'the initial interval charging'increments thereafter effective on capacitor C-l start at a 'predetermined capacitor voltage.

The foregoing delay in discharge of C-'3 by shut-otfof tube T-4 is not present when the now moving laneca'rs have been holding the right of way against waiting cars on the stopped lane (i. e., when relay R-l vdroppedout before relay R-2 dropped out to close contacts 43, 43a).

It may now be noted that vehicle extension intervals demanded by cars approaching in the moving lane -A do not accumulate, but each extension vinterval cancels the remaining portion of the preceding interval vand re-starts the timing of a `single extension interval. Thisisbecause of the fact that upon each actuation kthe lane A timing capacitor C-l is always charged up to a Ypredetermined maximum voltage determined by the setting of 'potentiometer'26a, 26h, 26e, 26d.

Referring now again to the transfer operation effected by discharge of the capacitor C-3 through the resistor 28, it may be noted that the resistor 28 is preferably "of relatively low resistance so that the capacitor C3 discharges throughthis resistor in about one second. Upon suchfdischarge, the extension limit timing tube T-'3 is krendered conductive so that the associatedplate relay R-3 is picked up and closes its 'normally open contact 47, thereby to complete an energizing circuit for the drum advance motor S from the power supply line L-2 to ground.

It will now be evident Athat if cars approaching on *the initially moving lane A had continued `to demand Vehicle extension intervals, i. -e., no suicient break in 'lane yA traic to permit expiration of an extension interval, the contacts 34, 34b of the lane Afplate relay R-l would have remained open Vso that the capacitor C-3 could not vdischarge through the rapid transfer resistor 23. Eventually, however, the capacitor C-3 would have vbecome discharged through the extension limit resistor 16 which is connected across this capacitor by the drum contact'Cs. Thus, veither `because ofexpiration of the extension limit time or because of a breakin lane Amoving traiic, the extension limit timing `tube T-3 is rendered conductive as described, 'therebyto pick up its plate relay and energize the motor "5 to advance the drum.

It may be here noted that when transfer of the Yright of'wayis effected bythe presencevof lane B waiting cars beforethe lane A limiting time has expired and by reason of 'a break in lane A trai-lic, the transfer is 'effected -by rapid discharge of C-3 through resistor l28. This discharge takes a short time, for example, one second, so that if during this discharge a car actuates the detector on the green lane A, such car takes preference over the cars waiting on lane B in that the lane A plate -relay R-i .is again dropped out 'for one extension interval to ylinterrupt at contacts 34, 34b discharge of capacitorfC-S through resistor 28. lSuch preference, however, is not gi-venwh'en transfer is eiected by discharge of C-3 through 'there-X- tension limit resistor 'because'this discharge isfno't affectedby cars on the 'streethavingfthe right of way.

VAdvance of thedrum 4 toward position 4imrnediately closes the drumcontact'Cv, thereby to pick up the vtransfer relay TR-4 and open 'the cathode circuit forthetiming tube T-3. Thisrenders -the tube T-3 nonconductive so :that the plate relayR-S is droppedout `andthernotor 5,.deenergized. By reason of a capacitor 48 .connectedin series with a rec'tier 49 across the lmotor 5, and a resistor 50 shunting the rectier 49, a charge stored inthe .capacitor 48 discharges through the motor, thereby to .brake the motor .to a stop atposition 4 of thetdrum. This motor braking circuitlismorefully describedandfclaimedinmy copending patent application, Serial No. 271,799, tiled February 15, 1952, for Electric Motor Braking Systems. When the drum arrives at position 4, it completes another motor energizing circuit operative to drive the drum to position 5, as will be later described, so that the drum only pauses briefly in position 4.

Pick-up of relay 'TR-4 in drum position 4 also completes a charging circuit for the extension limit timing capacitor C-3. This charging circuit may be followed from the potentiometer Sa (or 8 in the opposite right of way condition at drum position 12), through the relay contacts 10, b, contacts 51, Slb on relay 'fR-4, the grid-to-cathode space of tube T-3, the capacitor C-3, and the voltage divider 7.

It will be observed from the drum diagram that in this position 4 of the drum the green light on lane A is deenergized and the amber light substituted therefor. T he red light still remains on lane B. It will be further observed that through -drum contact C1 the A transfer relay TR-l is dropped out, thereby to remove the resistor 12 from its shunt circuit relation with the capacitor C-l and prepare the capacitor C-l for the accumulation of an initial interval charge as heretofore described in connection with capacitor C-2. The drum contact C7 is closed in position 4 as heretofore described. Furthermore, the drum contact C9 is closed in position 4, thereby to energize the transfer relay TR-3. When the transfer relay TR-3 picks up, it transfers its selector contact 10 from 10a to 10b thereby to transfer the charging circuit for the extension limit timing capacitor C-3 from a lane A potentiometer 8 to a lane B potentiometer 8a. The transfer relay "fR-3 also transfers its contact 31 thereby to close the contacts 31,`31b and open the contacts 31, 31a, thus associating the discharge resistor 27 with lane A rather than with lane B. The purpose and operation of resistor 27 will be described hereinafter. Transfer relay TR-S also transfers a contact 52 from 52a to 52h thereby to transfer control of the cathode circuit of the timing tube T-3 to the lane A rather than the lane B plate relay. Finally, the relay TR-3 transfers a pair of contacts 53 and 54 to transfer certain capacitor charging circuits from lane A to lane B operation, as will hereinafter become more evident, and transfers a contact 5S. This contact 55, as Well as contacts 56 and 57 (now transferred by relay TR-4), introduces a memory feature into the operation as will be hereinafter more fully described.

Finally, advance of the drum to position 4 closes the drum contact C12, thereby to complete an energizing circuit from the power supply line L-2 to the motor 5 and advance the drum from position 4 to position 5.

In position 5, no change is effected in the lighting circuits nor in the other drum contact positions so that the motor 5 remains energized through the drum contact C12 and thus advances the drum to position 6. This position is thus a dummy position provided to facilitate the use of a standard sixteen-position drum.

In position 6, the motor 5 is deenergized at the contact C12 and brakes to a stop through the circuit 48, 49 and 50. In this position 6, there is still no change in the lighting circuits, but it will be noted that drum contacts C4 and C5 are now closed and drum contact C7 opened. The drum contact C4 energizes the transfer relay TR-6, and the drum contact C7 drops out relay TR-4, which opens its contact 51, 5117 to interrupt the charging circuit of capacitor C-3 and prepare the tube 'I`-3 for conduction. The drum contact C5 completes the cathode circuit of the amber timing tube T-S.

Amber timing-Referring first to the amber timing circuit, it will be observed that the cathode circuit for the amber timing tube T-5 is completed only in drum positions 6, 7, 8 and 14, 15, 16. The tube T-S is therefore non-conductive in all other drum positions. At Fig. 2, I have shown a simplified circuit diagram of the amber timer circuit alone, using the same reference numerals as at Fig. 1 and showing principally the components involved in transfer of the right of way from lane A to lane B.

It will rst be noted that prior to closure of the contact C5 a charging circuit is complete for the capacitor C-S of the discharge tube T-5, which circuit may be followed from the power supply line L-2, through a voltage divider 58, the capacitor C-S, the grid-to-cathode space of the discharge tube T-S, a resistor 59, the contacts 15, 15b of the transfer relay TR-S, and a potentiometer 60. (A similar potentiometer 61 is connected by contacts 15, 15a if lane B amber is being timed.) The potentiometers 6l) and 61 and the voltage divider 58 are so set that when the line L-1 is positive, the tap 58a on the voltage divider 5S is negative with respect to the slider 60a on the potentiometer 60 (or the slider 61a on the potentiometer 61). When the power supply line L-1 is negative, the point 58a is positive with respect to the slider 61M (or 61a) and grid current flows through the discharge device T-S to charge the capacitor C S to the difference Voltage between the points 58a and 60a (or 61a). The capacitor C-S thus stands charged at the time that the drum moves into position 6. Thus, when the drum contact C5 closes, the potentiometer 60 is shunted by resistor 59. The negative charge on the capacitor C-S now leaks olf through resistor 62 and is reduced to the potential difference between that of the power supply line L-2 and the point 58a on the voltage divider 58. During the decay of the charge on capacity C-S, the amber timing tube T-5 is retained nonconductive. When the capacitor C-S is discharged sufficiently so that the amber timing tube T-S becomes conductive, the associated plate relay R-S is picked up, thereby to close a normally open contact 63 and cornplete an energizing circuit for the duim advance motor 5. When the amber timing plate relay R-S is picked up, it also closes another normally open contact 64 which completes a minimum interval charging circuit for capacitor C-2 (or C-1 as the case may be) as will be more fully described hereinafter. Thus, the drum is advanced from position 6 to position 7.

Referring back now to the closure of the drum contact C4 when the drum arrived at position 6, it will be noted that this drum contact energized the transfer relay TR-6. When this relay is energized, it transfers several. selector contacts 65, 33 and 66. Transfer of the contact 65 removes line L2 power from two detector timing relay contacts 67 and 68 and places L-2 power upon contacts 34 and 42 of the lane A and lane B plate relays, respectively. Transfer of the contact 38 removes connections of the line L-2 from the point 36 on the potentiometer 37a-37d and connects this line directly to contact 54h on the transfer relay TR-3, and thus through the contact 54 on 'fR-3 (now picked up) and the amber plate relay contact 64 (closed after the amber timing interval) on the contact 53 of the transfer relay TR-3, thereby to prepare for minimum initial interval timing for lane B as will be more fully described hereinafter.

The drum now having advanced to position 7, it will be noted that still no change is effected in the lighting circuits, and that no change is effected in any other of the drum contact circuits except the drum contact C12, which is now again closed. Closure of the contact C12 insures energization of the drum advance motor 5 so that the drum advances to position 8.

At drum position 8, the lighting circuits are still unaffected, but the drum contact Cs is closed. Closure of the drum contact Ca again connects the maximum extension limit timing resistor 16 across the extension limit timing capacitor C-3, thereby to prepare for the timing of another extension limit interval. In position S, the drum contact C12 is still closed so that the drum advance motor 5 is still energized and the drum advances to position 9.

In position 9, the drum contact C5 is opened so that lthe cathode circuit of the amber discharge tube T-S is interrupted, thereby to interrupt conduction of this timing tube, whereupon its plate relay R-S drops out, thereby to open the contact 63 and 64. In drum position 9 also, the green light for lane B is energized through the drum contact GB, the red light for lane B is deenergized at the drum contact RB, the amber light for lane A is deenergized at the contact AA, and the red light for lane A is energized through the Contact RA. In this position 9 of the drum, the drum advance contact C12 is also opened and the drum contact C11 closed. Closure of the contact C11 short circuits the portion 37b, 37C of the potentiometer 37a--37a- Difference interval-When the potentiometer 37a- 37d is thus partially short circuited, provision is thereby made for setting up the capacitor C-2 (which has thus far accumulated increments of initial interval charge) to time a difference interval. This difference interval is constituted approximately of the accumulated initial interval less one vehicle extension interval, and has for its purpose to eiectively increase the lane B extension limit time in accordance with cars stored on the now green lane B between the light and the detector (these cars having arrived on lane B VWhile red) in the same manner as if they had arrived on line B while green. This is necessary because cars stored on lane B (now green) behind the detector do not have an opportunity to increase the extension limit by crossing the lane B detector (as further described hereinafter) until the cars ahead of the detector are cleared.

The foregoing difference interval is prepared in position 9 in the following manner. In this position, relay TR-2 is picked up, as hereinafter pointed out, and relay TR-6 is also picked up as previously pointed out. By this action, contacts 38, 38a of relay TR- and contacts 69, 69a of relay rl`R-2 disconnect the capacitor C-2 from the normal charging voltage point 36 on potentiometer 37a-37d. Also, closure of contacts 69, 69h of relay rl`R-2 shunts the portion of potentiometer 37a-37d through a small capacitor 70 and a resistor 71 in series and connects capacitor C-2 to the common point of capacitor 70 and resistor 71. (A capacitor 7a and resistor 23 are similarly connected to potentiometer 26a- 26d in transfer of right of way from lane B to lane A.) At the same time, drum contact Cn is closed so that the charging-potential on capacitor C-2 is now determined in effect by the slider 72 on potentiometer 37a-37d. Now therefore, if the slider 72 is higher in potential than the accumulated voltage on capacitor C-2, then tube T-2 conducts immediately in drum position 9. Iny this case, the difference interval is not effective. If, however, the potential of slider 72 is less than the. accumulated negative voltage of capacitor C-2 (i. e., many cars are stored on lane B), then tube T-2 is maintained non-conductive only until the stored capacitor voltage decreases by leakage to equal the potential of Slider 72. This represents the difference interval. During this difference interval, the cathode circuit of tube T-4 is interrupted at contacts 65, 65a of relay TR-G, thereby to extend the extension limit time, as will be later pointed out.

In this drum position 9 also, the drum contact C10 is closed, thereby to complete an energizing circuit for the lane B transfer relay TR-Z. When the transferv relay TR-Z picked up, it closed its normally open contacts 69, 69h thereby to connect the discharge resistor 41 across the lane B timing capacitor Ce2. It will be recalled that the timing capacitor C-Z was previously charged in increments by cars approaching on lane B when that lane had the red light, such accumulated charge representing the initial interval. This capacitor, therefore, is retaining the grid of the tube T-Z negative and that tube non-conductive. When the resistor 41 is connected across the capacitor C-Z by energization of the transfer relay TR-Z, the capacitor C-2 begins to discharge. As described 14 above, this discharge takes place only down to the point where the voltage of C-2 equals that of potentiometer slider 72 (i. e., if slider 72 is at the initially higher voltage). That is, the timing tube T-2 is maintained nonconductive for a difference interval determined by the extent of the charge previously accumulated on the capacitor C-2 and the voltage of slider 72. When tube T-2 conducts, relay R-Z picks up, thereby to lenergize the drum motor 5 through a circuit which may be followed from the motor through contacts 32, 32a of relay R-4, a contact 73 of relay TR-Z, contacts 42, 42b of relay R-2, and -contacts 65, 65b of relay TR- to L-2 power. The drum 4 therefore advances to position 10.

Initial interval timing-In drum position 10, no change is effected in the lighting circuits. The drum contact C4 is opened. The drum contact C11 is also opened, and the drum contact C3 is opened. Opening of the drum contact C3 disconnects the plates of the lane A and lane B timing tubes T-1 and T-2 from the power supply line L-1 so that these tubes cannot become conductive in drum position 10. This drum position 10, however, is only a transfer position, for in this position the drum contact C12 is momentarily closed, thereby again to complete an energizing circuit for the drum advance motor 5 and move the drum to position 11. In position 11, the energizing circuit for the motor 5 is interrupted by re-opening of the drum contact C12 and the plate circuits of the discharge tubes T-1 and T-2 are reconnected to this power supply line L-1 by -reclosure of the drum contact C3. l

In this drum position 11, the tube T-Z is now maintained non-conductive because of the negative charge still remaining on the capacitor C-2 (i. e., not dissipated during the difference interval and representing the remainder of the initial interval for lane B). So long as the discharge device T-2 is non-conductive, no transfer of the right of way to lane A can be initiated because of the dropped-out position of the associated plate relay R-2. The reason for this is similar to the description hereinbefore of the manner in which drop-out of the lane A plate relay R-1 for vehicle extension intervals precluded transfer of the right of way to lane B for such extension intervals.' Briefly, it will be recalled that so long as the plate relay R-l or R-Z of that lane having the green light is dropped out, dis-charge of the extension limit timing capacitor C-3 through the rapid discharge capacitor 28 is precluded. In this drum position 11, therefore, the relay R-2 picks up at the termination of the remainder of the initial interval (or at the termination of such interval plus one or more vehicle extension intervals if they are demanded by cars approaching on lane B). The tubes T-1 and T'-2 are now in their normal conductive conditions for lane B right of way, just as for lane A right of way in drum position 3.

Rest.-It will now be recalled, and may be further observed by inspection of the drawing, that position 11 on the drum is a normal or rest position in which the right of way is granted to lane B, in the same manner as position 3 is a rest position in which right of way is granted to lane A. It will thus be evident that with the drum in position 11 the right of way is on lane B so that the timing capacitor C-2 may be recurrently charged as a result of actuations of the lane B detector 2, thus pre- -cluding transfer of the right of way for predetermined vehicle extension intervals; while vehicles approaching the intersection on the now stopped lane A effect incremental charging of the timing capacitor C-1, thereby to store an initial charge in this capacitor for discharge to determine an initial vehicle interval when the right of way is restored to lane A.

It will be further evident that return of the right of way from lane B to lane Av by transfer of the drum from position 11 to position 3 takes place in a manner similar tothat described above, for transfer of the drum from position 3 to position 11, so that no further description of this action is deemed necessary. Those skilled in the art will now appreciate that certain circuit components identified by reference numerals on the drawing but not specically referred to in the operation are useful only in this second half cycle, and their correspondence of function to components already described will be readily discerned from the drawing and description.

The initial and extension interval timing circuit for tube T-l and drum position 3 is shown in simplified form at Fig. 5, using the same reference numerals as at Fig. l. The operationwill be fully understood from the foregoing description of Fig. 1.

In view of the foregoing description of the operation, certain other features of loperation not previously mentioned may now be more readily followed.

Extension limit time decrease It may first be noted that the extension limit time determined by discharge of the capacitor C-3 through the large extension limit resistor 16 is not a fixed time, but is subject to reduction in response to the approach of vehicles on the stopped lane. This is done by momentarily connecting the discharge resistor 27 in parallel circuit relation with the resistor 16 each time that a vehicle approaches the intersection on the stopped lane, thereby more rapidly to discharge C3 in recurring increments. It may be observed that such parallel connection is effected either through the contact 29 of the lane A detector relay D-l, or the contact 30 of the lane B detector relay D-Z, one or the other of these contacts being selected by the contact 31 on the transfer relay 'TR-3. For example, in position 1l where lane A is stopped, the relay TR-3 is energized through the drum contact C9 so that the contact 3l is closed on the contact 31h. The lane B detector relay contact 30 is therefore disconnected from the circuit and the stopped lane A detector relay contact 29 is connected in circuit, thereby to connect the discharge resistor 27 in parallel circuit relation with the resistor 16 momentarily each time that the detector relay D-1 is picked up for a predetermined impulse interval by the detector 1 on lane A. In this manner, the extension limit interval for which the green light may be held by cars approaching the intersection on the moving lane is progressively reduced as more and more cars accumulate between the intersection and the detector on the stopped lane.

Extension limit time increase In addition to the foregoing, the extension limit time determined by the discharge of capacitor C-3 through resistors 16 and 27 is subject to increase in response to cars approaching the intersection on the moving lane by the operation of the extension limit increase timing tube T-4 in the following manner. The extension limit increase circuit of Fig. l is shown in simplified form at Fig. 3, using the same reference numerals as at Fig. l and showing only components used with lane A green.

Not previously mentioned was the fact that the timing tube T-4 is normally Vconductive so that its plate relay R-4 is normally picked up, thereby normally to connect a discharge resistor 74 in parallel circuit relation with the extension limit resistor 16. The cathode circuit for the timing tube T4 may be followed from the cathode through the selector contact 13 on the transfer relay TR-S and then through one or the other of the detector timing relay contacts 67, 68, to the power supply conductor L-Z through the transfer contact 65 on the transfer relay TR-6. Thus, except when the relay TR-6 is picked up in positions 6, 7, 8 and 14, 15, 16, the discharge tube T-4 is conductive. It will be noted also that the discharge tube T-4 is provided with a grid capacitor Ced across which is shunted a discharge resistor 7S, one end of the capacitor C-4 being connected to an intermediate point 76 on a potentiometer 77a, 77h, 46. Thus, if either of the detector timing relays DT-l or DT-Z is picked up, the contact 67 or 68 connects the cathode of the discharge device T-4 to the sliderv 77 on the potentiometer 77a, 77h, 46 on the opposite side of ground from the point 76.

It will now be evident that in operation the extension limit increase timing tube T-4 is normally conducting. Upon actuation of the detector in the moving lane, for example, in drum position 11 on lane B, the detector relay D-2 is picked up and the detector timing relay DT-il is picked up. When the relay DT-Z is picked up, the cathode circuit of the tube T-4 is interrupted at the contact 68 and the same contact connects the cathode of the tube T-4 to the point 77 on the potentiometer 77a, '77b, 46. This causes the capacitor C-4 to be charged on half cycles when the line conductor L-2 is positive, thereby to render the grid of the discharge tube T-4 negative. Thus, when the detector relay D-Z and the detector timing relay DT-Z again drop out after a predetermined impulse interval, the tube T4 is retained non-conductive sufficiently long for the predetermined charge to leak off the capacitor C-4. During this short timing interval, the plate relay R-4 is dropped out, thereby to discon neet the discharge resistor 74 from its normal parallel circuit relation with the extension limit resistor 16. In this manner, the rate of discharge of the extension limit capacitor C-3 is temporarily reduced, thus increasing the extension limit interval in response to detector actuations on the moving lane.

Ultimate extension limit time It will now be evident that even though cars approaching on the stopped lane are able progressively to decrease the extension limit time by connecting the resistor 27 in parallel circuit relation with the resistor 16, and cars on the moving or green lane are able progressively to increase the extension limit time by disconnecting the resistor 74 from its normal parallel circuit relation with the resistor 16, the resistor 16 itself being connected across the capacitor C-3 only by the drum contact Ca, insures that an ultimate limiting time is always imposed for discharge of the capacitor C-3 once the timer has been started in operation. Stated in another way, the extension limit interval increase and decrease resistors 74 and 27, respectively, merely decrease or increase the rate of discharge of the capacitor C-3, but do not in any event recharge the capacitor. Thus, the extension limit interval timer (including tube T-3) always possesses an ultimate time limit characteristic, despite the fact that the limiting time may be increased by cars approaching the green light.

This ultimate discharge time is, of course, not of fixed predetermined duration, but depends upon trac conditions. The ultimate limit is, of course, simply a mode of operation of the extension limit timer, so that for any particular tratiic condition the limit time is fixed. In the extreme case, if no cars approach onrthe street having the red light, and if cars approach continuously on the street having the green light, continuous effort is made to increase the extension limit time by removing resistor 74 from the discharge circuit of capacitor C-3. Even though resistor 74 is, continuously held Vdisconnected, and resistor 27 never connected in circuit, the capacitor C-3 will ultimately discharge through capacitor 16 and will impose an ultimaterlirniting time. Under the one extreme condition assumed, of course, this ultimate time is predetermined.

Fig. 4 shows a simplified circuitdiagram of the extension of transfer timerT- for one half rcycle of operation, using the same reference numerals as at Fig. 1.

Minimum initial interval timing Attention is now directed to a feature of initial interval charging not heretofore mentioned. ,It will be recalled that the initial green interval onY any lane has been described as being timed by recurrent incremental chargafferisce ing of the timing capacitor (C-1 or C-2) associated with that lane by cars approaching on that lane when it has the red light. This is done by recurrently picking up the stopped (i. e., red) lane detector relay (D-l or D-Z) for a predetermined impulse interval upon each vehicle actuation on the stopped Such pick-up momentarily completes a charging circuit which may be followed, for capacitor C-Z for example, from the resistor 40 through contacts 3d, 39a on relay TR-2, contacts 35, 35h on relay D-Z, the grid-tocathode space of tube T-Z, the capacitor C-2 and a resistor 7S to line L-Z. (A similar resistor Ida is provided for the lane A timing tube T-1.)

ln the event such charging increments do not add up to a charge of predetermined minimum voltage, representing a predetermined minimum initial interval, means are provided to bring the charge always to such minimum value. This is done for the respective phases by means of variable potentiometers 79 and d0, the operable po tentiometer for each lane operation being selected by the contact 53 on relay TR-3. A charging circuit for initial interval charging is completed during right of way transfer operation. For example, for transfer from lane A green to lane B green, transfer relay TR-6 is picked up in drum positions 6 9, inclusive, to complete a charging circuit for capacitor C2 which may be followed from the slider 79a of potentiometer 79 through contacts 53, 53h of relay 'fR-3, contact 64 of amber plate relay R-S (which picks up in drum position 6 after timing the amber display), contacts 54, 54b of relay 'FR-3, contacts 38, 38]) of relay "fR-6, capacitor (2 2, the grid-tG-cathode space of tube T-Z, and contacts 35, 33a of relay D-1 to line L-Z. The like operation for reverse transfer of the right of way will be evident to those skilled in the art.

Memory feature Attention is now directed to the memory function of contacts '5, 56 and 57 on relays 'TR-3 and TR-d. If the right of way is transferred from lane A by reason of expiration of the extension limit time before the end of a vehicle extension interval then running on lane A, then when the drum is passing through positions 4 and 5, detector relay D-l is picked up through contacts 44, 44a of relay R-l, contacts S2, 52h of relay TR-3, contacts S6, 56h of relay 'fR-1i, contacts 55, 5512 of relay 'TR-3, and contacts 17, 17a of relay D'lll, Pick-up ot' relay D-l stores a single increment of charge on capacitor C-1 in the same manner as if a car had approached on lane A against the red light. This extends the time for which right of way is restored to lane A by reason of the call already requested by the existing deenergization of relay R-l under such conditions. The same action takes place if a contact 31 on relay R-d is closed by reason of short interval drop-out of R-d whenever relay R-1. picks up. Thus, the short drop-out interval ol R- after R-l picks up (i. e., lane A extension expired) is included in the period during which memory may be registered.

Automatic recall lt will now be readily possible to appreciate the function and operation of the recall switches R1 and R2. In the foregoing description, it has been assumed that both recall switches were open. In this condition, the apparatus operates to retain the right of way on the street last called (i. e., floating). rfhis is because, when the recall switches are open, the cathode circuit of tube T-3 (the tube conduction of which initiates transfer) is not completed (through contacts d3, 43u of relay R-Z) until a red street actuation takes place.

However, with the recall switch Rt, for example, closed, the contacts lid, da of relay R1 are shunted so that switch R1 registers an automatic recall of right of way to lane A in the same manner as the memory operation described above. Switch R1 also completes the cathode circuit of tube T-3 so that T-3 will conduct to initiate a re-transfer of right of way to lane A as soon as all eX- 1S tension time on lane B has expired (i. e., C-3 is discharged) despite the fact that no actuation has occurred on lane A to drop out relay R-l.

Similarly, an automatic recall is placed in drum position 3 by closure of switch R2. l'f both switches Rt and R2 are closed, cyclic standby operation results, and it will be evident that if no cars approach on either street with both R1 and R2 closed, the cyclic right of way time on each street is the minimum initial interval time previously described.

Semi-actuated apparatus At Fig. 6, I have illustrated certain features of my invention as embodied in a semi-actuated traflic signal control apparatus. The apparatus illustrated at Fig. 6 is applicable to the intersection of a pair of traffic lanes, and it will be understood from the foregoing that only the minor lane B is provided with a detector.

The apparatus illustrated at Fig. 6 bears a general resemblance to that illustrated at Fig. l in that there is provided a vehicle detector 101 adapted to be positioned beneath or adjacent the roadway on the minor traiiic lane B, a signal indicating device 102, a rotatable signal sequence drum 103, and a plurality of electronic timing tubes T-ll, T-3l, T-lll and T-Sli for controlling the advance of the drum to vary the display of signal lamps in response to actuations of the detector. The signal sequence drum 193 is connected to be advanced in steps by a motor 16d having a braking circuit 105' similar to that shown at #i3-S0 ol' Fig. l. As at Fig. 1 also, the signal sequence drum 1113 is provided with six signal lamp switches RA, AA, GA, RB, AB, and GB. In addition, the drum is provided with a plurality of other cam switches C2i, C22, C23, C24, C25, C26 and C27 which are operable in conjunction with the various timing circuits in a manner which will hereinafter be explained.

The controller of Fig. 6 includes four electronic timers each including a grid controlled electron discharge tube, such as the three-element vacuum tubes 1111, Te31, T-41 and T-Sl. The timing tube T-ll is arranged to time the initial interval and vehicle extension intervals for the minor lane B. The timing tube T-31 is in an extension limit and transfer timer and corresponds in a general way to the timing tube T-3 of Fig. 1. The extension limit timing function of the tube T-31 is applicable only to the minor lane B in the case of Fig. 6. The timing tube T-41 is in an extension limit increase timer and corresponds in a general way to the timing tube T-4 of Fig. l; and the timing tube T-'Sl is in an amber timer for both streets and corresponds to the timing tube T-S of Fig. l. In addition, the timing tube T-31 opcrates to time a xed initial or minimum interval for the major lane A. As will hereinafter appear, means are provided in the apparatus of Fig. 6 for incrementally reducing this lane A minimum time in response to actuations of the Vdetector 101 on lane B when that lane is stopped.

As in the apparatus at Fig. l, each of the timers including the tubes T41, T41, T-41 and T-51 includes also a grid capacitor which when charged maintains the tube nonaconductive, and one or more discharge resistors adapted to be connected across the capacitors. Specically, the tube T-ll is provided with a grid timing capacitor C-11, the tube T31 is provided with a grid capacitor C-31, tube T-ll is provided with a grid capacitor C-41 and the tube T-S1 is provided with a grid capacitor C-51. In addition, the timing tubes are provided with anode or plate relays iii-11, R-31, R-41, and R-Sl, respectively. The detector lill is connected to control a detector timing relay DT-ll, and the relay DTll is connected to control a detector relay D-ll. Impulse timing of the relay DT-11 is accomplished by a simple series capacitor 107. In addition, there are provided three transfer relays r.FR-11, TR-Zll and TR-31 controlled 'respectively by the drum contact C22, C25,

and RB. Power is supplied to the timers, relays, lights and drum motor from a transformer T-1 through power supply lines L-1 and L-2, the center of the transformer secondary winding being grounded.

Semi-actuated operation-General The interaction of the various timers and relays in controlling the advance of the sequence drum 103, and additional functions of the timers and relays will be more readily understood by proceeding now to describe the operation of the device under typical conditions of traffic actuation.

In the embodiment of the invention shown at Fig. 6, the signal sequence drum 103 is provided with six switching positions representing one complete cycle of operation. Since the apparatus is of the semi-actuated type, only a single position of the drum is a normal rest position. The normal rest position is position 1 in which it will be noted that the green signal is granted to the major lane A through the drum switch GA, and the red signal is displayed to the minor lane B through the drum switch RB. It will be evident, of course, that since no detector is provided in the major lane A, the drum will remain in position 1 and no change will be eifected in the signal display so long as no tratiic approaches on the minor lane B, regardless of the amount of traic o-n the major lane A. In addition to the rest position 1 of the drum, the drum is provided with a dwell position (position 4), in which the right of way is accorded to lane B for a time determined by the density of traffic o-n lane B, as will appear hereinafter.

Fig. 6 reverting- Transfer lane A lo lane B position 1 and that no traffic actuations have taken place for a considerable length of time so that the entire apparatus is in a steady-state or standby condition. In this condition, the initial and extension interval timing tube for lane B, T-11, is conductive since the lane B recall switch R21 (closed for reverting operation) connects the cathode of T-11 to line L2, and the timing capacitor C-11 is connected to a point 122 on potentiometer 123a, 123b, 123C, which point is positive with respect to line lf2 when line L-l is positive. The discharge tube T-31 is also conductive. This is because the cathode is connected directly to the supply line L-2 through drum co-ntact C24, and the grid is connected through the capacitor C-31 to a point 110 on a potentiometer 109er, 109b, 109C, the point 108 being positive with respect to L-2 when L-1 is positive. The discharge tube T-41 is maintained conductive for a similar reason, i. e., the cathode is connected directly to L-2 through contacts 135, 135a on relay T11-21, while the grid is connected to a point 112 on a voltage divider 115e, 115b, 115C. The discharge tube F1-51 is maintained non-conductive, both because its cathode circuit is open at the drum contact C27, and because a potentiometer 116:1, 116i), 116C is connected between the cathode of tube T-51 and the capacitor C-Sl through a resistor 117 and the contacts 118, 118b of the relay TR-31 in a manner to maintain the grid negative with respect to the cathode when the line L-l is positive.

With the discharge tubes in the foregoing condition, it will be observed that the anode relays R-11, R-31 and R-41 are picked up, and the anode relay R-51 is dropped out. In addition, it will be noted that the drum contacts C-24, GA and RB are closed. The drum co-ntact C-24 connects the cathode of discharge tube T-31 to the line L-2. The drum contact GA energizes the green light for lane A. The drum contact RB energizes the red light for lane B and also energizes the relay TR-31.

If now a vehicle actuation is received upon the minor and stopped lane B, the detector switch 101 is closed momentarily, thereby to complete an energizing circuit for the detector timing relay DT-11 from the supply line L-2 through a rectifier R', the switch 101, a capacitor 107, a resistor 119, and the actuating coil of the relay DT-11. The relay DT-11 is energized only so long as current flows through this circuit to charge the capacitor 107. A resistor 132 shunting capacitor 107 is so large that insufficient current flows through it to hold the relay DT-ll picked up. While the relay DT-11 is thus picked up for an impulse interval, it closes its contact 120, thereby to complete an energizing circuit from the supply line L-Z for the actuating coil of the detector relay D-11. When the relay D-11 picks up, it opens its normally closed contacts 121, 121a and closes its normally open contacts 121, 121b. Opening of the contacts 121, 121a interrupts the cathode circuit for the discharge tube T-11 and renders this device non-conductive so that the plate relay R-11 drops out.

When the normally open contacts 121, 121k of the relay D-11 are closed, a charging circuit is completed for the capacitor C-11, which circuit may be followed from a point 122 on a potentiometer 123g, 12317, 123C, through the capacitor C-11, the grid-to-cathode discharge space of the tube T-11, the contacts 121, 121]? of the relay D-11, and through the contacts 124, 124m of the relay TR-li to the slider 140a of a potentiometer 140. Through this chargingcircuit, a single impulse or increment of charge is placed upon the capacitor C-11 during the interval while the relay D-11 is picked up. This charge times a single vehicle initial interval for the lane B right of way, as will hereinafter appear.

Drop-out of the plate relay R-ll, as previously described, closes a normally closed contact 126 and also opens the normally open contact 127. Opening Contact 127 has no effect at this time since, when closed, it was not included in any closed circuit. Closing of contact 126 completes an energizing circuit for the motor 104 from the supply line L-2 through the contact 130 of relay R-31, contacts 131, 131a of relay 'FR-21 and the Contact 126. The motor 104 being energized, the drum advances from position 1 to position 2.

In drum position 2, no change is effected in the lighting circuits, as will be evident from the diagrammatic representation of the drum, but the drum contacts C21, C23, C25 and C26 are closed, while the drum contact C2.; is opened. Closure of drum contact C21 shunts the detector switch 101, thereby again to pick up relays DT--11 and D-11 for a second impulse interval and thus to add a second increment of initial interval charge to capacitor C-11. This automatic charging impulse insures a sutilcient initial interval in the event that right of way is returned to lane B by the memory circuit described hereinafter.

Closure of the drum contact C23 short circuits a resistor' 112 in the charging circuit of the capacitor C-31. @pening of the drum contact C24 interrupts the cathode circuit of the discharge tube T-31 thereby to render this device non-conductive and to render the charging circuit for C-31 operable. Closure of the drum contact C25 com'- pletes an energizing circuit for the relay TR-21. This relay therefore picks up and remains energized through drum positions 2, 3 and 4 as will appear from the drum diagram. When the relay TR-21 picks up, it closes its contacts 11141111, thereby to transfer the charging circuit for the extension limit timing capacitor C-31. This charging circuit may now be followed from the point on the potentiometer 109a-109c through the capacitor C31, the grid-to-cathode discharge space of the timing tube T-31, the drum contact C23 and the contacts 111, 11111 on the relay 'fR-21 to a slider 132 on a potentiometer 133 connected in parallel circuit relation with the potentiometer section 109:1. Through this charging circuit, the capacitor C-31 is charged to a voltage representing an extension limit interval with the right of way on lane B. Drop-out of the plate relay R-31 and consequent opening of the Contact 130 interrupt the drum motor ener- 2i gizing circuit so that the motor is braked to' a stop at position 2. The motor 104 is, however, again energized in drum position 2 by closure of drum contact C26 so that the drum is advanced from position 2 to position 3.

When the drum 163 moves to position 3, the green light on lane A is deenergized and the amber light on lane A is displayed through the drum contact AA. In this position, phase A amber is timed and the drum is next advanced in position by operation of the amber timing tube T-Sl.

In drum position 3, it may first be observed that drum contact C21 is open, thereby to interrupt the energizing circuit for relay DT-11, which relay, however, was already dropped out by action of the blocking capacitor 107. The relay D-11, being dropped out, completes the cathode circuit of the discharge tube T-11. This discharge tube does not, however, conduct since the capacitor C-11 is now negatively charged and provided with no discharge path. In this drum position 3 also, drum contact C23 opens, thereby to unshunt the charging resistor 112. The drum contact C24 is reclosed thereby to reconnect the cathode of the discharge tube T31 to the negative power supply line L-Z, and thus permits the capacitor C-31 to begin discharging through resistor 129 and 12951 in parallel, thereby to time the lane B extension limit interval. p

Amber timing-ln addition to the foregoing, drum contact C27 is closed in drum position 3, thereby to connect the cathode ofthe amber timing tube T-Sl to the power supply line L-2. With the cathode thus connected, however, the tube T-51 does not immediately conduct because the capacitor C-51 stood negatively charged by reason of its connection to the potentiometer 116a-116c through the resistor 117 and the contact 118, 118b of relay Til-31. Capacitor C-Sl now begins to discharge through the parallel-connected resistor 136 to time the amber display interval. When the capacitor C-51 is suiciently discharged so that the grid-to-cathode voltage is substantially zero on positive half cycles of supply potential, the discharge tube T51 conducts and energizes its plate relay ETSI. When the relay R-Sl picks up, it closes its normally open contact 137 thereby to complete an energizing circuit for the motor 104 and advance the drum from position 3 to position 4.

ln drum position 4, the green light is displayed on lane B, the red light interrupted on lane B, the amber light interrupted on lane A, and the red light displayed on lane A, as will be evident from the diagrammatic illustration of drum switches GB, RB, AA and RA. 1n drum position 4 also, the drum contact C27 is opened thereby to interrupt the cathode circuit of the timing tube T-51 and render this tube non-conductive. Opening of the drum switch RB also deenergizes the relay TR-31 so that this relay drops out and closes its contacts 11.8, 118m. Transfer of the contact 118 by relay T11-31 substitutes for the potentiometer section 11611 in the charging circuit of capacitor C-S, a potentiometer section 138 connected in parallel circuit relation with the section 116a. Potentiometer 13S is adapted to determine a charge on the capacitor C-il suitable for timing the amber interval on lane B, as will hereinafter appear, while potentiometer 115g determines the lane A amber interval.

Initial and extension timing-In drum position 4, drum contact C22 is closed thereby to complete an energizing circuit for the transfer relay TRell. When the relay rlR-lli picks up, it closes its contact 139a thereby to connect across the timing capacitor C-11 a discharge resistor 139. The capacitor C-11 begins immediately to dissipate its negative charge, thereby to time the initial right of way interval for lane B, as will be evident from the foregoing description of Fig. 1. It will now be evident that any additional lane B detector actuations which took place in drum positions 1, 2 or 3, while the green or amber lights were displayed on lane A and the red light on lane B, will have repeatedly energized the detector relay D-11 for short impulse intervals deter@ mined by the capacitor 107, thereby to store in the capacitor C-11 additional increments of charge, the accumulated total of which determines the initial interval for the right of way on lane B. It will hereinafter become evident that such initial interval charge for lane B also accumulates in drum positions 5 and 6.

Pick-up relay TR-ll also transfers its contact 124 from 124g: to 124b, thereby to substitute in the charging circuit of the capacitor C11 a potentiometer section 123e for the potentiometer previously referred to. This provides a new charging circuit for capacitor C-11, adapted to determine vehicle extension intervals whenever relay D-11 is picked up by cars approaching on lane B while it has the right of way. Thus, each actuation of detector 101 when lane B has the right of way picks up relays DT-11 and D-11 for a single impulse interval in the manner already described. Relay D-11 when picked up interrupts the cathode circuit of tube T-11 at contacts 121, 121a and completes a charging circuit for capacitor C-11 at contacts 121, 121b. The capacitor C-11 is thus charged to a voltage representing a single vehicle extension interval and retains the tube T-11 nonconductive for such interval. This action is repeated by each vehicle approaching on lane B when it has the right of way. It will be understood that so long as tube T-11 is non-conductive, the relay R11 is dropped out and precludes re-transfer of the right oi way to lane A because contact 127 of relay R-11 is thus held open to prevent short circuiting and rapid discharge of extension limit capacitor C-31 (which is presently discharging slowh ly through resistors 129 and 129e to time the vehicle eX- tension limit interval).

It may now be noted, also, that whenever the detector 101 is actuated to pick up the relays DT11 and D-11 for an impulse interval while lane B has the right of way, not only is an extension interval charge stored in capacitor C-11, but the tube T-41 is rendered non-conductive for a timed interval to increase the extension limit time. This is because in drum position 4 with lane B green the cathode of tube '1%41 is normally connected to L-2 through the contacts 135, 135b of relay TR*21 and the normally closed contact 134 of detector relay D-11. When contact 134 is momentarily opened by an actuation, the cathode circuit of tube T-41 is broken and the tube rendered non-conductive. In this condition, the capacitor C-41 is negatively charged by grid conduction on half cycles when L-1 is negative so that when contact 134 of relay D-11 reconnects the cathode of tube T-41 to line L-2, the tube r1141 remains non-conductive until the capacitor C-41 discharges through its shunting resistor 140. During the interval while tube T-41 is thus shut 01T, the plate relay R-41 is dropped out and opens its contact 141 to unshunt the extension limit resistor 129, as described in connection with Fig. 1, thereby to increase the extension limit time.

The drum is moved off of position 4 when the timing tube T-11 again becomes conductive as determined by the discharge interval of the capacitor C-11. Now, therefore, when the initial interval charge and all extension interval charges on the capacitor C-11 are dissipated, the tube T-11 is again rendered conductive. When the discharge tube T-11 becomes conductive, the plate relay R-11 is picked up, thereby to open the contact 126 and close the contact 127. Opening ofthe contact 125 has no effect, but closing of the contact 127 completes a short circuit around the extension limit timing capacitor C-31, thereby immediately to discharge the capacitor C-31 and render the timing tube T-31 conductive. This short circuit may be followed from the grid of the tube r[-31, through the contacts 128, 128b of the transfer relay TR-21 and the contact 127 of the relay R11 to the other side of the capacitor C-31.

Extension limit timing-It may here be noted that in the event that vehicles continue to actuate the detector 101 while lane B has the right of way and with sufficient frequency that vehicle extension intervals are continuously demanded in Overlapping relation so that the timing tube T-11 never does become conductive, the extension limit capacitor C-31 eventually becomes discharged through the extension limit timing resistors 129, 129e. The tube T-31 is therefore rendered conductive either by reason of conduction of the tube T-11 after expiration of the initial and all vehicle extension intervals (and consequent short circuiting of capacitor C-l), or by reason of the discharge of capacitor C-31 through the extension limit resistors 129, 129:1.

When the tube T-31 thus becomes conductive as described, its plate relay R-31 is picked up and closes its contact 130. With the transfer relay Til-21 now in its energized position, closure of the contact 130 completes an energizing circuit for the drum advance motor 1&4, which circuit may be followed from the power supply line L-Z through the Contact 135, the contacts 131, 13112 of the relay T11-21, and the drum advance motor 104 to ground. The motor 104 thus being energized, the drum 103 is advanced from position 4 to position 5.

Mininmm l1tervCll.-ln drum position 5, the drum contact C22 is opened, thereby to deenergize the transfer relay rI`R-11. When the relay Til-11 drops out, it transfers its contact 124 to reconnect the charging circuit of the capacitor C-11 to the potentiometer 140, the initial interval charging potentiometer. The drop-out of the relay TR-11 also opens the contacts 139g, thereby to interrupt the discharge circuit of the timing capacitor C-11. ln drum position 5, the drum contact C25 is also opened, thereby to deenergize the transfer relay 'TR-21 and restore it to its initial position, described in connection with drum position l. As further appears from an examination of the drum diagram, movement of the drum to position effects no change in the lighting circuit but opens the drum contact C24 and closes the drum contact C23. Opening of the contact C24 interrupts the cathode circuit of the discharge tube T-31, thereby to render this tube non-conductive, drop out the plate relay R-31, and open the motor energizing contact 139. Mornentary closure of drum contact C23 completes a charging circuit for capacitor C-31 from the potentiometer 109m. Through this circuit, capacitor C-31 is charged to a voltage representing a minimum right of Way interval on lane A, in much the same manner as it is charged through drum contact C22 in drum position 2 to the maximum extension limit voltage. In drum position 5, however, the energization of the motor 104 is maintained through closure of the drum contact C26. The drum therefore advances from position 5 to position 6.

Drum position 6 is the lane B amber interval, and the drum remains in this position for a length of time de termined by the operation of the amber timing tube T-51. It will be noted that in drum position 6 the red light remains on lane A but the green light is discontinued on lane B and the amber light on lane B substituted therefor. Opening of thc drum contacts C in drum position 6 interrupts energization of the drum advance motor 104, so that the motor is braked to a stop in position 6.

In drum position 6, the drum contact C23 is opened and the drum contact C24 closed, thereby to reconnect the cathode of the tube T-31 to the power supply line L-Z and initiate discharge of the timing capacitor C-31 through the resistors 129 and 12961 in parallel. The discharge interval of the capacitor C-31 which is thus initiated represents the minimum right of way interval for lane A.

In drum position 6 also, the drum contact C27 is closed thereby to complete the cathode circuit for the amber timing tube T-S1. The amber timing capacitor C-51 thus begins to discharge through the resistor 136 from the charging voltage determined by the potentiometer 138, in the same manner as it previously discharged in drum position 3 from the voltage determined by the potentiometer 116e. The discharge tube T-Sll thus remains non-conductive in drum position 6 until the capacitor C-51 is discharged. This discharge represents the amber timing interval for lane B. When the capacitor C-51 is discharged, the tube T-Sl becomes conductive, thereby to energize its plate relay R-51 and complete an energizing circuit for the drum advance motor 16-4 through the contacts 137. The motor 164 thus being energized, the drum advances from position 6 to position 1. In drum position l, the drum contact C27 is opened, thereby to interrupt the cathode circuit for the tube T-51 and render that tube non-conclue tive. Drop-out of the associated plate relay R-Sl interrupts the motor energizing circuit and the motor 1M is braked to a stop in drum position l.

Rest-In drum position l, the right of way is on lane A. Lane A is not provided with a detector so that no initial interval or vehicle extension intervals are operative in connection with the lane A right of Way interval. As previously noted, however, a minimum right of way interval for lane A is provided by charging the capacitor C-31 from potentiometer 1t9a in drum position 5. Until this charge is dissipated, the discharge tube T-31 cannot become conductive and the plate relay R-31 remains dropped out. So long as the relay R-31 is dropped out, its contact is open and no energizing circuit can be completed for the drum advance motor 104, even though the tube T-11 is rendered non-conductive by actuation of the lane B detector. in this connection, it will be recalled that transfer from drum position 1 to drum position 2 is effected by completing a motor energizing circuit through. the Contact 130 of relay 1?.-31, the contacts 131, 131a of relay TR-Zl, and the contact 126 of relay R-11, all in series circuit relation. The Contact 130 thus being held open for a lane A minimum interval, closure of contact 126 by vehicle actuations on lane B cannot immediately effect transfer of the right of Way. Transfer is effected, however, as soon as the lane A minimum interval expires so that tube 31 is ren dered conductive and the contact 13'() closed.

Minimum interval reduction It may now be noted, however, that during the passage of the lane A right of way minimum interval, the minimum interval may be shortened by actuations of the detector 101 on the stopped lane B. As previously noted, the lane A minimum interval is determined by discharge of the capacitor C-31 through resistors 129 and 12911 in parallel. it will now be observed that with the transfer relay TR-21 in its dropped-out position, momentary pick-up of the detector relay D-11 for an impulse interval upon each actuation of the lane B detector completes, through a contact 142, a shunt circuit for the capacitor C-31 through a resistor 143. This shunt circuit may be followed from the grid of the tube T-31 through the contacts 128, 128g of the relay TF1-21, the contact 142 of the relay D-11, and the resistor 143 to the other side of the capacitor C-31. Thus, whenever the lane B detector 161 is actuated during the lane A minimum right of Way interval, the resistor 143 is momentarily connected in parallel circuit relation with the discharge resistors 129, 12.9(1, thereby momentarily to accelerate the discharge of the capacitor C-31. 1n this manner, vehicles approaching the stopped lane B during the lane A minimum right of way interval are effective to decrease this minimum interval in increments.

It will now be evident to those skilled in the art that if the lane A right of way minimum interval expires without any actuation of the detector 1111 on lane B, the apparatus is again in the standby condition with which the description of the operation was initiated.

25 Memory recall Let it now be supposed, however, that the retransfer of the right of way to lane was elfected by operation of the extension limit, rather than by expiration of all vehicle extension intervals on lane B, so that a vehicle is still on lane B between the detector and the light. In this case, the timing capacitor C-11 would have been only incompletely discharged at the time that the drum was moved off position 4, and its discharge circuit broken. The tube T-Il thus remains non-conductive throughout drum positions S and 6, and is still non-conductive in drum position l when the lane A minimum interval expires. The tube T-ll thus being non-conductive, its plate relay R-l is dropped out and the plate relay contacts 126 close. Therefore, when the lane A minimum interval expires and the tube T-Sl is rendered conductive, pick-up of the associated plate relay R-31 completes, by closure of the contact 30, a drum motor energizing circuit in the same manner as that initially described when drum position 1 was first considered. It will now be evident that in this memory type recall operation, the small negative charge still remaining upon the timing capacitor C-lll may not be suiicient to permit the vehicle stored on lane B to be cleared. It is for this purpose that the capacitor C-11 is recharged in drum position 2 through closure of the drum contact C21 as previously described.

Fig. 6.-Cyclc Finally, it will now be observed that normally cyclic operation of the controller shown in Fig. 6 may be effected by opening the recall switch R21. When the switch R21 is opened, the cathode circuit of the tube T-ll is interrupted so that the plate relay R-l remains dropped out at all times, thereby to leave the contacts 126 continuously closed. Continous closure of the contact 126 acts as a recall of the right of way to lane B so that the apparatus continually goes through a cyclic alternation of the right of way, even in the absence of vehicle actuation. It will, of course, be appreciated that during this cyclic operation, actuation of the lane B detector 101, while lane A has the right of way, reduces the lane A minimum interval, in the same manner previously described. Similarly, actuations of the lane B detector i when lane B has the right of way introduce vehicle extension intervals and increase the lane B extension limit time in the same manner previously described.

Operation at intersection of more than two trac lanes it will now be evident to those skilled in the art that my new and improved controller is equally applicable to intersections of three or more traic lanes, or streets. For example, in the full actuated controller of Fig. l, it is only necessary to provide, for a three-street controller, a twenty-four position drum controller, another initial and extension interval timer connected in parallel with the timers which include tubes T-l and T-2, and transfer relays having, in proper circumstances, three rather than two selector positions. The timing tubes T-3, T-4 and T-S, being common to all lanes, may readily be transferred between three streets in like manner as they are shown transferred between two streets. It is, of course, additionally necessary to provide a third pair or" detectors and a third detector relay and detector timing relay, these also being connected in parallel relationship with the like components illustrated. Thus, by simple paralleling of additional similar components, itis clearly possible to utilize my controller for intersections of two, three or more intersecting traiiic lanes. It will be similarly evident that the semi-actuated controller of Fig. 6 may be expanded in like manner to control intersections of more than two streets, detectors and initial interval timers being provided in such case for all except the one main street or lane.

While I have described only certain preferred embodiments of my invention by way of illustration, many modilications will occur to those skilled in the art, and I therefore wish to have it unlerstood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a vehicle actuated traic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting trac lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, means controlled by said vehicle actuated device when said lane has said stop indication for actuating said signal switching means to accord said go indication to said lane, timing means controlled by said vehicle actuated device when said lane previously had said stop indication for predetermining au initial go indication interval on said one lane, means responsive to each actuation of said vehicle actuated device when said one lane has said go indication for controlling said timing means to extend said go indication beyond said initial interval and until a predetermined time after said actuation, and separate timing means controlled by said switching means and operable after a limiting interval to render said rst timing means ineffective to extend said go indication and to operate said signal switching means to remove said go indication from said one lane.

2. In a vehicle actuated traiiic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, means actuated by each vehicle approaching said device on a lane having a go indication to extend said go indication, timing means operable after a limiting interval to render said extending means ineffective, and means actuated by each vehicle approaching said device on a lane having a go indication to increase said limiting interval.

3. In a vehicle actuated trali'ic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, vehicle actuated devices on at least two of said lanes, means controlled by a vehicle actuated device on a lane having a go indication to extend said go indication, separate timing means operable after a limiting interval to render said extending means ineffective, and means concurrently controlled by all said vehicle actuated devices for incrementally controlling the length of said limiting interval.

4. In a vehicle actuated traiic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traitic lanes, signal switching means connected to accord said go indication successively to said lanes, means actuated by a vehicle approaching said device on a lane having a go indication to extend said go indication, timing means operable after a limiting interval to render said extending means ineliective, and means actuated by each vehicle approaching said device on a lane having a stop indication to reduce said limiting interval.

5. In a vehicle actuated tra'ic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traiiic lanes, signal switching means connected to accord said go indication successively to said lanes, means actuated by each vehicle approaching said device on a lane having said go indication to extend said go indication, timing means operable after a limiting interval to render said extending means ineffective, means actuated by each vehicle approaching said device on a lane having a go indication to increase said limiting interval, and meansactuated by each vehicle approaching said device on a lane having a stop indication to reduce the said limiting in- 27 terval then running on the lane having said go indication.

6. In a vehicle actuated trac signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, an electron discharge device having an anode, a cathode and a control electrode, means responsive to conduction of said discharge device for actuating said signal switching means to transfer said go indication from one lane to another, timing means including a capacitor connected to said control electrode for maintaining said discharge device non-conductive when said capacitor is charged, means controlled by said vehicle actuated device when Said one lane has said go indication for charging said capacitor to a predetermined voltage upon each vehicle actuation, and second timing means for rendering said first timing means ineffective to extend said go indication and for actuating said signal switching means to remove said go indication from said one lane after a limiting right of way interval.

7. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, an electron discharge device having an anode, a cathode and a control electrode, means responsive to conduction of said discharge device for actuating said signal switching means to transfer said go indication from one lane to another, timing means including a capacitor connected to said control electrode for maintaining said discharge device non-conductive when said capacitor is charged, means controlled by said vehicle actuated device when said one lane has said stop indication for incrementally charging said capacitor to a voltage proportional to the number of vehicles actuating said vehicle actuated device, means controlled by said vehicle actuated device when said one lane has said go indication for charging said capacitor to a predetermined voltage upon each such vehicle actuation, and second timing means for rendering said first timing means ineffective to extend said go indication and for actuating said signal switching means to remove said go indication from said one lane after a limiting right of way interval.

8. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, means controlled by said vehicle actuated device when said one lane has said stop indication for actuating said signal switching means to accord said go indication to said lane, second switching means for actuating said signal switching means to remove said go indication from said one lane, first time element means for disabling said second switching means, means controlled by said vehicle actuated device for controlling said first time element means to retain said go indication on said one lane for at least an initial interval after accord of said go indication, means responsive to each actuation of said vehicle actuated device when said one lane has said go indication for controlling said first time element means to extend said go indication for a predetermined interval following each said actuation, and second time element means for rendering said first timing means ineffective to extend said go indications and for energizing said second switching means to remove said go indication from said one lane after an extension limiting interval.

9. ln a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting trac lanes, signal switching means connected to accord said go indication successively to said lanes, means actuated by a vehicle approaching said device on at least one of said lanes when said lane has said stop indication for actuating said signal switching means to accord said go indication to said one lane, first timing means controlled by said signal switching means to retain said go indication on said one lane for at least an initial interval, means responsive to each additional actuation of said vehicle actuated means while said one lane has said go indication for controlling said first timing means to extend said go indication, second timing means controlled by said signal switching means for rendering said first timing means ineffective to extend said go indication and for operating said signal switching means to remove said go indication from said one lane after an extension limiting interval, and means responsive to each said additional actuation for incrementally increasing said extension limiting interval.

10. in a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lines, a vehicle actuated device on at least one of said lanes, means controlled by said vehicle actuated device when said one lane has said stop indication for actuating said signal switching means to accord said go indication to said one lane, second switching means for actuating said signal switching means to remove said go indication from said one lane, first timing means for disabling said second switching means, means controlled by said vehicle actuated device when said one lane has said stop indication for controlling said first timing means to retain said go indication upon said one lane for at least an initial interval after accord to said one lane, means responsive to each additional actuation of said vehicle actuated device while said one lane has said go indication for controlling said first timing means to extend said go indication for a predetermined interval after each such actuation, second timing means controlled by said signal switching means for rendering said first timing means ineffective to extend said go indication and for rendering said second switching means effective to remove said go indication from said one lane after an extension limiting interval, and means responsive to each said additional actuation for incrementally increasing said limiting interval.

1l. In a vehicle actuated trafic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traflic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, means controlled by said vehicle actuated device when said one lane has said stop indication for actuating said signal switching means to accord said go indication to said one lane, second switching means for actuating said signal switching means to remove said go indication from said one lane, first time element means for disabling said second switching means, means responsive to actuations of said vehicle actuated device when said one lane has said stop indication for controlling said first time element means to maintain said go indication on said one lane for at least an initial interval after accord thereto, means responsive to each actuation of said vehicle actuated device while said one lane has said go indication for controlling said first time element means to extend said go indication for a predetermined interval following each such actuation, second time element means controlled by said signal switching means for rendering said second switching means effective to remove said go indication after a predetermined extension limiting interval, and means responsive to each said last-named actuation of said vehicle actuated device for incrementally increasing said extension limiting interval.

12. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traiiic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each said lane, second switching means controlled by the vehicle actuated device on a stopped lane for operating said signal switching means to accord said go indication to that lane, first timing means controlled by the vehicle actuated device on each lane prior to accord of said go indication to that lane to retain said go indication on that lane for at least an initial interval after accord of said go indication, second timing means controlled by the vehicle actuated device on a moving lane for rendering said second switching means ineffective to operate said signal switching means for an extension interval after each moving lane actuation, third timing means controlled by said signal switching means for rendering said second timing means ineffective to extend said go indication after an extension limiting interval, and means controlled by said vehicle actuated device on a moving lane to incrementally increase said extension limiting interval. l

13. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each said lane, second switching means controlled by the vehicle actuated device on each lane when stopped for actuating said signal switching means to accord said go indication to that lane, an electron discharge device controlled by the vehicle actuated device in each lane and each including an anode, a cathode and a control electrode, means controlled by said signal switching means for connecting the discharge device associated with a moving lane when conductive to render said second switching means effective to remove the go indication from that lane, means responsive to the vehicle actuated device on a moving lane for controlling the control electrode potential of the associated discharge device to render said discharge device non-conductive for a predetermined interval following each such vehicle actuation, timing means for rendering said second switching means effective to remove said go indication from a moving lane after an extension limiting interval independently of conduction of the associated discharge device, and means responsive to each actuation of said vehicle actuated device on a moving lane for controlling said timing means to incrementally increase said extension limiting interval.

14. In a vehicle actuated trafiic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, electroresponsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a first to a second lane, a capacitor connected when charged to maintain said control electrode negative with respect to said cathode thereby to render said discharge device nonconductive, a resistor connected across saidr capacitor to control the discharge thereofV thereby to time an interval, a second resistor adapted to be connected in shunt circuit relation with said first resistor, and means controlled by vehicles approaching said signal device on at least one of said lanes for controlling said shunt circuit connection thereby to control the rate of discharge of said capacitor and the'length of said interval.

l5. In a vehicle actuated trafic signal control apparatus including a signal device providing stop and go indications for each ofv a plurality of intersecting tratic lanes, electroresponsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge, device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a first to a second lane, a capacitor connected when charged to maintain said control electrode negative with respect to said cathode thereby to render said discharge device nonconductive, a resistor connected across said capacitor to control the discharge thereof thereby to time an interval, and means controlled by vehicles approaching said signal device on at least one of said lanes for momentarily connecting in shunt circuit relation with said resistor a second resistor thereby incrementally to reduce the length of said interval.

16. In a vehicle actuated traic signal control apparatus including a signal device providing stop and go indications for each of a plurality of Aintersecting traflic lanes, electroresponsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a first to a second lane, a capacitor connected when charged to maintain said control electrodenegative with respect to said cathode thereby to render said discharge device nonconductive, a resistor connected across said capacitor to control the discharge thereof thereby to time an interval, and means controlled by vehicles approaching said signal device on at least one of said lanes for momentarily disconnecting said resistor from said capacitor thereby to reduce the rate of discharge of said capacitor and incrementally increase the length of said interval.

17. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traiiic lanes, electroresponsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a first to a second lane, a capacitor connected when charged to. maintain said control electrode negative with respect to said cathode thereby to render said discharge device non-conductive, a resistor connected across said capacitor to control the discharge thereof thereby to time an interval, a second resistor normally connected in shunt circuit relation with said first resistor, and means recurrently actuated by each vehicle approaching said signal device on a moving lane for momentarily disconnecting said second resistor thereby to reduce the rate of discharge of said capacitor and incrementally increase the length of said interval. Y

18. In a vehicle actuated trafiic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, electroresponsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a first to a second lane, a capacitor connected when charged to maintain saidcontrol electrode negative with respect to said cathode thereby to render said discharge device non-conductive, a resistor connected across said capacitor to controlthe discharge thereof thereby to time an interval, a second resistor, and means recurrently actuated by vehicles approaching said signal device on a lane having said stop indication for momentarily connecting said second resistor in parallel circuit relation with said capacitor thereby to increase the rate of discharge of said capacitor and incrementally'to decrease the length of said interval.

19. In a vehicle actuated traiic signalv control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, electro-responsive signal switching means connected to accord said go indication successively to said lanes, an electron discharge device having an anode, a cathode and a control electrode, means operable upon conduction of said discharge device to actuate said signal switching means to transfer said go indication from a rst to a second lane, a capacitor connected when charged to maintain said control electrode negative with respect to said cathode thereby to render said discharge device nonconductive, a resistor connected across said capacitor to control the discharge thereof thereby to time an interval, a second resistor adapted to be connected in shunt circuit relation with said first resistor, a third resistor normally connected in shunt circuit relation with said first resistor, means recurrently actuated by vehicles approaching said signal device on a lane having said stop indication for momentarily connecting said second resistor in shunt with said first resistor thereby to increase the rate of discharge of said capacitor and incrementally to reduce said interval, and means recurrently actuated by vehicles approaching said signal device on a lane having said go indication for momentarily disconnecting said third resistor from said capacitor thereby to decrease the rate of discharge of said capacitor and incrementally to increase said interval.

20. In a vehicle actuated traic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting trac lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each of said lanes, means controlled by the vehicle actuated device on a stopped lane for operating said signal switching means to accord said go indication to said stopped lane, means controlled by the vehicle actuated device on a moving lane for rendering each vehicle actuated device on a stopped lane ineffective to operate said signal switching means for an extension interval after each moving lane actuation, timing means controlled by said signal switching means for rendering said means responsive to actuations on a moving lane ineffective after an extension limiting interval, and means responsive to each actuation of the vehicle actuated device on a stopped lane for controlling said timing means to incrementally decrease said extension limiting interval.

2l. In a vehicle actuated trac signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each of sai-d lanes, second switching means controlled by the vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to that lane, rst timing means for disabling said second switching means, means actuated by the vehicle actuated device ou a stopped lane for controlling said first timing means to maintain said second switching means disabled for at least an initial interval after said go indication is accorded to said lane, means actuated by the vehicle actuated device on a moving lane for controlling said rst timing means to maintain said second switching means disabled for a predetermined extension interval following each moving lane actuation, second timing means controlled by said signal switching means for operating said second switching means independently of said rst timing means after an extension limiting interval, and means actuated by the vehicle actuated device on a stoppedv lane for recurrently and incrementally decreasing said extension limiting interval.

22. In a vehicle actuated trac signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traffic lanes, sinal switching means connected to accord 4said go indication successively to said lanes, vehicle actuated devices on all except one of said lanes, means controlled by a vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to said stopped lane, means controlled by said signal switching means to thereafter return said go indication to said one lane, timing means controlled by said signal switching means and effective upon such return of said go indication to said one lane to render said vehicle actuated devices ineffective to actuate said signal switching means for at least a minimum right of way interval, and additional means controlled by said vehicle actuated devices during said minimum interval to reduce said interval in increments in response to each vehicle approaching the signal device on a stopped lane.

23. in a vehicle actuated tratlic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting trac lanes, signal switching means connected to accord said go indication successively to said lanes, vehicle actuated devices on all except one of said lanes, means controlled by the vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to said stopped lane, means responsive to each actuation of the vehicle actuated device on a moving lane for extending the go indication then accorded to that lane, means controlled by said signal switching means for returning said go indication to said one lane, timing means controlled by said signal switching means and effective upon such return of said go indication to said one lane to render said vehicle actuated devices ineltective to actuate said signal switching means for at least a minimum right of way interval, and additional means controlled by said vehicle actuated devices during said minimum interval to reduce sai-d minimum interval in increments in response to each vehicle approaching the signal device on a stopped lane.

24. In a vehicle actuated traic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traic lanes, signal switching means connected to accord said go indication successively to said lanes, vehicle actuated devices on all except one of said lanes, means controlled by a vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to said stopped lane, means responsive to each actuation of a vehicle actuated device on a moving lane to extend for a predetermined interval beyond such actuation the go indication then accorded to that lane, timing means operable upon accord of said go indication to a lane to disable said extending means after a limiting time interval, means responsive to each actuation of the vehicle actuated device on a moving lane during said limiting time intelval for incrementally increasing said limiting time interval, means controlled by said signal switching means to return said go indication to said one lane, second timing means controlled by said signal switching means and effective upon such return of said go indication to said one lane to render said vehicle actuated devices ineffective to actuate said signal switching means for at least a minimum right of way interval, and additional means controlled by said vehicle actuated devices during said minimum ,interval to reduce sai-d interval by increments in response to each vehicle approaching the signal device ona stopped lane.

25. In a vehicle actuated traffic signal control apparatus including a signal device providing stop and go indications for each of ay plurality of intersecting traic lanes, signal switching means connected to accord said go indication successively to said lanes, vehicle actuated devices on all except one of said lanes, electro-responsive means for actuating said signal switching means, an electron discharge device connected when conductive to energize said electro-responsive means, means controlled by a vehicle actuated device on a stopped lane for rendering attivista said discharge device conductive thereby to actuate saidl signal switching means to accord said go indication to said stopped lane, means controlled by said signal switching means for rendering said discharge device conductive thereby to actuate said signal s witching means to return said go indication to said one lane, time element means responsive to each actuation of a vehicle actuated device on a moving lane for maintaining said discharge device non-conductive for a predetermined time interval beyond such actuation thereby to extend the go indication then accorded to that lane, lirst timing means including a capacitor connected to control said discharge device and operable after a limiting time interval following accord of said go indication to a moving lane to render said discharge device conductive independently of said time element means thereby to actuate said signal switching means, means responsive to each actuation of a vehicle actuated device on a moving lane during said limiting time interval for controlling said capacitor to incrementally increase said limiting time interval, second timing means controlled by said signal switching means and effective upon such return of said go indication to said one lane to maintain said discharge device non-conductive for at least a minimum right of way interval, and additional means controlled by said vehicle actuated devices during said minimum interval to control said capacitor to reduce said minimum interval in increments in response to each vehicle approaching said signal device on a stopped lane.

26. in a vehicle actuated traic signal control apparatus including a signal device providing st op and go'indications for each of a pluralityof intersecting trafic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each of said lanes, second switching means controlled by the vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to that lane, first timing means controlled by the vehicle actuated device on a lane prior to accord of the go indication to that lane for retaining said go indication on that lane for at least an initial interval after accord of said go indication, second timing means controlled by the vehicle actuated device on a moving lane for rendering said second switching means inelective to operate said signal switching means for an extension interval after each moving lane actuation, third timing means controlled by said signal switching means for rendering said second timing means inelective to retain said go indication on a moving lane after an extension limiting interval, third switching means responsive to the vehicle actuated device on a moving lane for controlling said third timing means to incrementally increase said extension limiting interval, and fourth switching means responsive to the vehicle actuated device on a stopped lane for controlling said third timing means to incrementally decrease said extension limiting interval.

27. In a vehicle actuated traic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting trac lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each of said lanes, second switching means controlled by the vehicle actuated device on a stopped lane for operating said signal switching means to accord said go indication to that lane, first time element means controlled by the vehicle actuated device on a lane prior to accord of said go indication to that lane for retaining said go indica.- tion on that lane for at least an initial interval after accord of said go indication, second time element means controlled by the vehicle actuated device on a moving lane for rendering said second switching means ineiiective to operate said signal switching means for an extension interval after each moving lane actuation, an electron discharge device connected when conductive to actuate Vsaid signal switching means independently of said second time element means, a capacitor connected to control conduction of said discharge device, a pair of resistors connected in shunt circuit relation with vsaid capacitor to time a normall extension limiting interval after accord of said go indication to a lane, third switching means responsive to the vehicle actuated device on a moving lanev for momentarily disconnecting one of said resistors from said capacitor thereby incrementally to increase said extension limiting interval, and means responsive to a vehicle actu ated device on a'st'opped lane for momentarily connecting in shunt circuit relation with said capacitor a third resistor thereby incrementally to decrease said extension limiting interval. l

28. In a vehicle actuated tratic signal control apparatus including a signal device providing stop and go indications for each of a plurality'of intersecting traiic lanes,` signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on each of said lanes, second switching means controlled by the vehicle actuated device on a stopped lane for actuating said signal switching means to accord said go indication to that lane, irst timingl means controlled by the vehicle actuated device on a lane prior to accord of said go indication to said lane for'retaining said go indication on said lane for at least an initial interval after accord of said go indication, second timing means controlled by the vehicle actuated'device on a moving lane for rendering said second switching means inetective to actuate said signal switching means for extension interval after each`moving lane actuation, third timing means controlled by said signal switching means for rendering said second timing means ineffective to extend said go indication after an extension limiting interval, third switching means momentarily responsive to operation of the vehicle actuated device on a moving lane for controlling said third timing means to incrementally increase said extension limiting interval, fourth switching means momentarily responsive to the operation of the vehicle actuated device on a stopped lane 'for controlling said third timing means to incrementally reduce said extension limiting interval, and means forming part of said third timing means for predetermining an ultimate extension limiting interval operable despite' substantially cQntinuOuS .Operation of said third switching means.

29. In a vehicle actuated tratic signal control apparatus including a signal device providing stop and go indications for each of a plurality of intersecting traic lanes, signal switching means connected to accord said go indication successively to said lanes, a vehicle actuated device on at least one of said lanes, second switching means controlled by said vehicle actuated device when said one lane has said stop indication for actuating said signal switching means to accord said go indication to said 'one lane, tirst timing means controlled by said vehicle actuated device on said one lane when said one lane has said stop indication forlpredetermining a subsequent initial right of way interval for said one lane proportional to the number of vehicle actuations on said lane when stopped, second timing means controlled by said vehicle actuated device on said lane when Vsaid one lane has said go indication for rendering said rst switching means ineffective to remove said go indication for at least a predetermined extension interval after each moving lane vehicle actuation, third timing means for actuating said signaly switching means to remove said go indication from said one lane independently of said second timing means after an extension limit interval, and second switching means controlled by said vehicle actuated means on said one lane when said one ,lane has said stop indication for initiating timing operation of said third timing means- 3(). In a vehicle actuated traflic signal control apparatus including a signal device providing stop and go indications for each af a plurality of intsrsetins fra lanes,

Images