US2761119A - Traffic control system - Google Patents

Description

8, 1956 J. BARKER ET AL TRAFFIC CONTROL SYSTEM 2 Sheets-Sheet 1 Filed Dec. 4, 1953 N No.2

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INTERCONNECTING LINES TO OTHER LOCAL CONTROLS IN VENTOAS.

JOHN L. BARK? ATTORNEY Aug. 28, 1956 J BARKER ET AL 2,761,119

TRAFFIC CONTROL SYSTEM Filed Dec. 4, 1955 2 Shee ts-$heet 2 INVENTORS. JOHN L. BARKER BY WILLIAM G. PENNELL LDSG) L03 FIG. 3 2 a? 7/53 ATTORNEY master frequency of one frequency line more than the other. Another feature of the invention is that the split alone may be changed without increasing the total cycle, by increasing the frequency on one channel while decreasing it correspondingly on the other, or the split and the total cycle may both be changed by increasing or decreasing the frequency on both channels but by different amounts for example, or by increasing or decreasing the frequency on one channel without changing the frequency on the other channel.

This remote control of split as well as cycle length has special significance in connection with conversion from a progressive signal system to a simultaneous signal system as is sometimes required in the heaviest trafiic conditions. Simultaneous systems ordinarily employ not only a much longer cycle than the progressive systems but also a much higher proportion of the total cycle on the through street.

It is therefore a general object of the invention to provide an improved traffic control system for varying by remote control the total length of the green periods and of the signal cycle or the split of the cycle or both for one or more trafiic signals.

It is another object of the invention to provide an improved traffic control system in which the relative proportion of the respective green signal periods for the intersecting roads and individual trafiic signals is determined jointly by settings of the individual controllers and by remote control from a common master controller over a wide range of adjustment.

It is a further object of the invention to provide a trafiic control system in which a series of individual trafiic .signal controllers are operated through the respective green signal periods of their cycle at time rates separately adjustable by separate variable frequency driving power channels made eifective by each local controller in its respective green periods, the separate frequency channels being supplied and separately adjusted by a single common master controller.

It is a still further object of the invention to provide a master-local control system for traffic signals employing two variable frequency power sources for the local controllers supplied by and separately controlled by the master controller for varying the total signal control cycle and the split of such cycle between the respective green periods, with means at the local controller for rendering the respective frequency sources effective for control of i the local controller signal cycle for the respective green signal periods, together with means at the master controller for operating a master cycle resynchronization unit at correspondingly varying time rates from the respective variable frequency power sources during different' parts of the cycle of such resynchronization unit, to maintain the cycle of the latter unit at approximately the same length as the cycle of the local controllers, the resynchronization unit cooperating with means at the local controllers for cyclically resynchronizing the local controllers with the master controller.

Other objects of the invention Will appear from the accompanying claims and the following description with respect to the drawings in which:

Fig. 1 illustrates in block diagram form the more general features of a traflic signal system according to one aspect of the invention.

Fig. 2 illustrates in schematic form a master control apparatus for a trafiic control system according to one embodiment of the invention, and providing output master control lines for control of the local signal controllers.

Fig. 3 illustrates in schematic form a set of traffic signal-circuits and associated local control apparatus for one intersection along the highway or roadway, with the connection with the master control apparatus of 4 Fig. 2 for a trafiic control system according to one embodiment of the invention.

Referring now to Fig. l in more detail a trafiic control system having a common master controller with two variable frequency generators in the broken line block designated Master control is indicated at the top of this drawing, with their output lines for the two frequency channels extending downward for a series of individual local signal controllers along a highway for example.

Two sets of local control equipment are indicated in block diagram form and in broken line blocks at the right, as illustrative of two intersections along the highway. Each set of local control equipment includes a local signal controller with input control lines from the two variable frequency lines and with an output line controlling a local amplifier above which in turn controls a local rotary dial unit to its right which in turn controls the local signal controllers which in turn control a trafiic signal. The local signal controller is also supplied by another input line from the local fixed frequency as indicated in the block below the local signal controller, this local fixed frequency serving to provide a constant period for the timing of the clearance signal intervals following the green signal intervals, independent of the variations of the green signal intervals and the total cycle, as will be more fully explained below.

Associated with the variable frequency generators at the master controller is a master cycle resynchronization unit which is controlled by connections from the respective variable frequency generator output lines and also by a fixed frequency supply indicated above this unit. A control line extends from the master cycle resynchronization unit downward in the drawing with connections to the individual local rotary dial units for resynchronization of the latter.

Referring now to Fig. 2 the master control apparatus is illustrated as comprising the two variable frequency generators within the broken line blocks VFGI and VFGZ, and the master cycle resynchronization unit or more briefly the master cycle unit indicated in the broken line block designated MCU, together with the several output lines illustrating the two variable frequency lines VFLI and VFLZ, with the common return for these lines at VFC, and resynchronization line and return RSL and RSR respectively. An auxiliary resynchronization reto make one or the other of the lines RSR or RSR effective as desired, the line RSR being connected with switch SW in the position shown.

A schematic circuit of one form of variable frequency generator is shown in each of the broken line blocks designated VFGI and VFG2, these variable frequency generators being similar but having reference characters identifying the several components with VFGI and VFG2 respectively. Referring to V-FGl as exemplary of both of the variable frequency generator units, there is provided a series motor designated MM1 and an associated A. C. generator GN1 driven by the motor MMl. The speed of the motor MM1 and the generator GN1 is varied by moving the tap PV1 along the resistance PR-l, thus providing an adjustable controlling resistancein series with the motor circuit via the motor coil indicated tion, with the several parts identified by the legend with the 2 ending instead of 1 as above, except-inthe d case of "the brushes which ate-identifiedidVFG2-as3f11 and 12'. These brushesof *the variable frequency generatrLV FG2 supply the variable rfrequeney line VFLZ and the common return VFC withits output frequency variable independently of that of -V' F G1.

The adjustment of the respective otentiometers PV'1- PR1 and 'PV2-PR2 may be madeby movinggthe re spective taps PVl and PV2 manually or by meanscfa time clock or other timing deviceyor by meansof one or more tra'ffic actuated cycle selectors or offsets'elector as in the Patent 2,542,978referred toabove for example, either smoothly or by 'StCPYtO' 'OHC 'Of' several tap,- ping positions along the respective resistances PR1 gand PR2 to vary the output frequency-on-therespective variable' frequency channels VPLI- and V'FL2 having the common return VFC.

I-t will be appreciated that while themotor-generator form ofvariable frequency generation is illustrated for simplicity, an electronic variable frequency generator may be used if desired, such as the familiar audio-frequency generator employed in electrical laboratories, in place of the motor-generator type of variable frequency'generator shown. AB. C. to A. C. converter or motor-generator with D. C. shunt motor d-riveandwith speed control by varying-the voltage applied to itsfield coils tor example, may be-alternat-ively employed as the variable frequency generator.

The mastercycle resynchronization unit MCU includes an amplifier MA- operated from the two variable frequency lines and from a fixed frequency power supply indifferent parts of its cycle, to repeat and amplify the variablefrequency power and preferably also the fixed frequency power to drive the master synchronous motor MSM'to rotatethe' cams MCl, MCZandMCR. The cams MCI and MC2 control, preferably by means of the intervening relays R1 and R2, theconnection of the input of the amplifier MA to the variable frequency line VFLI/during one part of the cycle and to the variable frequency line VFL2 inan-other part of the cycle, and to the fixed frequency source indicated by the transformer' FF during still another part of the. cycle; and the cam MCR controls the switch MSRto provide a cyclic resynchronization pulse over the line RSL and return RSR. The earns MC]. and MC2 control the Switches MSland M82 respectively, which in tu-rn control the relays R1 and R2 respectively to'connect the amplifier MA to the different frequency supply circuits in fthedilferent parts of the cycle of the master cycle unit MCU.

Inthe preferred form of this unit MCU illustrated in Fig. 2 the cams MCI and MC2 are arranged to close their respective cont-acts M81 and M32 each for substantially 50% of the cycle, the cams being shifted slightly from alternate halves of thecycle to provide abrief openper-iod for opening of both contacts M51 and M82 as shown in Fig.l 2 and a brief overlap period fortclosing both contacts M81 and M52 one half cycle awayfrom the-brief Openperiod. It will be appreciated that a different proportion such as.46% for closure of .MS1, another 46% for closure of M82 and 8% for opening of both contacts could be used if desired for example, with the same 50-50 division of operating time on the respective two variable frequency lines as above, where the local controllers have their rotary dials all. set for a basic equal division between the two go signal periods for equal frequencies on the two variable frequency lines.

.Inthe Fig. 2 arrangement, in theone .briefperiod in thecycle in wh-ich both of the contacts M81 and M52 are open, both ofthe relays R1 and R2 are deenergized. This is'wthe positionof the cycle illustrated in Fig. '2,-and in this condition the fixed frequency supply is connected to amplifier MA: and 'the variable frequency lines are disconnected from it. In the brief period ofclosure of both cor1tacts-MS1 and M52, bothrelayswill he energized andthe fixed frequency alone willbe connected to MA.

The two brief periods in the cycle-in :which-this condition of connection of fixed f-requency supply alone prev-ails correspond with the two yellow= clearance periods in, an ordinary trafiic signal cycle and each may represent some 4% of the cycle for example at the fixed frequency'driving rate The amplifier-MA has its input side connected-onone side via wire1 3to the variable'frequency return line VFC and on the other side via wire 14 :to movable contact Rll of relay Rl and thence through circ'uitscontrolled by this contact andthe contacts of relay-R2 which determine the connection of 'the appropriate frequency power-lines fordriving the amplifier. ThearnplifierMA has its output represented by the wires-15-and 16 which connect to opposite sides of the operating coil of motor MSM. The amplifier MA rthus repeats in amplified form the frequency applied to'its input to drive themotor-MSM fast or slow substantially in proportionitothe applied frequency, and-thus to rotate the cams MCI and M02 and MCR'fastor slow to provide a 'shorterorf longer-cycle respectively.

in gener'alinFigJZ and throughout the drawings-the symbolsplus in-aci-rcle landminus in a circledesignate the two terminalsof an alternating current power supply, which may for example be ordinary 60 cycle alternat-ing current power.

As the motorMSMrotateis, the corresponding rotation of cams M01 andMCQ will energize relays R1 or R2 with brief periods of deenergizationof both. relaysand of energization -ofboth relays intervening as -mentione'd above, andcam MCRawill open contact MSR'YIOI a -very brief part of the cycle.

With both relays R1=and -R2-deenergized as shown-in Fig." 2 the right side of the input of amplifier MA will be connected viawire l4,-contactsRll-Rltlof relay Rl, wire" 27, contacts R25-R26 ofrelay R2, wire '30, winding W2 offixed frequency supply transformer FF and wire 26 to the variable frequency return line VFC. The other winding-W1 of the fixed'frequency supply'transformer is connected-to the fixed frequencypower supply such as ordinary60 cyclealternating current for example. The transformer serves as a voltage matchingand isolating transformer and repeats the fixed frequency atthe desired voltage across its winding W2 and-consequently applies this frequency in the condition illustrated in'Fig. 2 via the circuit above traced to the input of the amplifier MA; 'Under'this condition the-amplifier is disconnected from the line VFLl because of separationof the contacts R11-.R12 of relay Rl and is disconnected from the-line VFLZbecause of separation of the contacts -R25--R24 of relay R2.

If it is now assumed'that the camsMCl and MCZ have turned. sufiiciently' for cam MCI to close its. contact MSI this will connect the plus power terminal via wire'31 to relay R1 and energize this relay since theotherside of the relay coil is connected totheminus power terminal. Relay RZ will remain deenergized however because cam M62 :will still keep its contact M82 open in the condition assumed, it having turned a'short distance in the counterclockwisedirection along with cam MCI and MCR. In the new condition assumed with-R1 energized and R2 deenergized the contacts Rll-a-Rn will now beclosed and the contacts R11+R1lb will now be open by the attraction of the movable contact R11 by therelay-Rl coil.

This change in contacts in this new position thenwill connect the input ofthe amplifier via wire lftycontacts R11-R12 now closed, wire 28, contacts RZl- RZfi and wire 25 to the first variable frequency line VFL L gthe previous connection to the fixed frequency power supply winding W2 having been interrupted by the separation of thecontacts'R11'-R10. In this assumed condition the amplifier MA is maintained disconnected from theg line VFLZ by; the scparatedcontacts "R25eRldrandifr-orn the fiXed frequency ndinsfWl a so rbvthei enara d contacts R21R22. i

If it is now assumed that the cams MCI, MC2 and MCR have turned still further through their cycle so as to have turned about 180 degrees from their initial position shown, both of the contacts M51 and M82 will be closed due to the overlap of the cams MCI and MC2, the latter each covering one-half of the cycle but having an overlap for a short distance by the cam lobes being slightly offset, leaving a corresponding open condition at the opposite side as shown in Fig. 2. Thus with the cams turned 180 degrees as now assumed and with both contacts M51 and M82 closed both relays R1 and R2 will be energized, the latter being energized via contact MS2 and wire 32, and consequently the movable contacts R11, R25 and R21 will ,allbe attracted downward by the relay coils. This will connect the input of amplifier MA via wire 14, contacts -R-11R12, wire 28, contacts R21R22 now closed, wire 29, to the fixed frequency supply at winding W2. The variable frequency line VFL1 will be disconnected at the separated contacts R11R10 despite the closed contacts R25-R24, and the line VFL2 will be disconnected by the separated contacts R21-R20.

It now however it is assumed that the cams are still further turned in a counter-clockwise direction so that cam MCI opens its contact M81 and cam MC2 retains its contact MS2 closed, then the relay R1 will be deenergized but the relay R2 will remain energized from plus power via wire 32, the other side of its coil being con- :nected to negative power. Such deenergization of relay R1 will release its movable contact R11 disconnecting it from contact R12 and connecting it to contact Rltl. In the condition now assumed the input of amplifier MA is connected via wire 14, contacts Rll-Rll), wire 27 and contacts R25-R24, wire 24 to the second variable frequency line VFL2, thus applying the variable frequency from this line to the input of the amplifier. The other variable frequency line VFL1 is disconnected from the amplifier by the separated contacts R2lR20, and the fixed frequency power winding W2 is disconnected from the amplifier by the separated contacts R25R26 and by the separated contacts Rl1-R12.

As the cams continue to turn they will complete their cycle to the initial condition shown,-and thus will continue to revolve through the ditferent parts of their cycle at speeds determined by the application of the several frequencies to the input of the amplifier by the action of the cams and their associated control switches and relays. In this connection, with the circuit arrangement shown the apparatus is protected. against the simultaneous connection of two different frequencies to the amplifier MA by the use of the relays and relay contact arrangements such that if both relays are energized or both relays are deenergized the fixed frequency power alone will be applied to the input of the amplifier, and despite any overlapping of the cams only one frequency at a time may be applied to the amplifier.

. The cam MCR preferably closes the contacts MSR throughout all but a very small part of the total cycle, and opens the contacts MSR during this small part of the cycle, for example a few seconds in length, so that one side of the power supply line indicated by the plus in a circle is connected to the resynchronization output line RSL during most of the cycle but is disconnected momentarily once per cycle for example. The return resynchronization line RSR is connected to the opposite side ofthe power supply as indicated by the minus sign in a circle, which may also be grounded as shown for example, with switch SW in its lower position shown. Switch SW may be changed to its upper position to connect line RSR to the negative power terminal in place of RSR if desired.

Referring now to Fig. 3, illustrating one form of local control apparatus and associated trafiic signal circuits,

. the lines extending across the upper part of this Fig. 3

and designated VFL1, VFL2, VFC, RSR, RSR and ESL are'extensions of the correspondingly designated output .8 lines to the right of Fig. 2, so that if the left side'of Fig. 3 is connected to the right side of Fig. 2, a complete master-local control system is illustrated. Although only one local signal controller is shown in Fig. 3 it will be appreciated that this will be illustrative of other local signal controllers which may be applied at other signalized intersections forming a part of a multiple intersection control system as indicated in the block diagram of Fig. 1. It will be appreciated in this connection that the several local controllers may be similar with the same cycle distributions, and with the same or a different relation of their green signal periods to the resynchronization point in their respective cycles, as controlled by the master cam MCR of Fig. 2 as more fully explained below.

These several master control lines at the top of Fig. 3 can be considered as extending along a highway or roadway for example common to several intersections having individual local controller units and associated traflic signals.

The signal circuits AG, AY and AR indicate circuits controlling the green, yellow and red signals for street A, and the signal circuits BG, BY and BR indicate the green, yellow and red signals for street B for example. These several signal circuits are controlled by the cam contacts or switches operated by several cams of a local step-by-step drum controller shown associated by broken lines with the ratchet drive wheel DRW.

This local drum controller may be one of several well known types of which the most common is a set of cams and cam operated switches for opening and closing the respective signal circuits as the cams are rotated by a motor drive which may preferably be of the step-by-step type widely used in tratfic signal controllers. One form of such step-by-step local drum controller is illustrated schematically in Fig. 3 for example.

The local drum controller includes the six cams CAG, CAY, CAR, CBG, CBY and CBR and their associated cam operated contacts immediately above for control of the signal circuits, together with the three cams CGl, CG2 and CY and their associated cam operated cont-acts immediately above for selection of the frequency supply circuits to be connected to the amplifier LA for operation of the local synchronous motor LSM in difierent parts of the cycle of the drum controller. The synchronous motor LSM drives a rotary dial assembly indicated by the dials LDl, LD2 and LD3 and their associated contacts immediately to the left for operating a solenoid ratchet drive in the step-by-step drum controller. The solenoid ratchet drive includes the solenoid DS which operates the live pawl LP to rotate the ratchet wheel DRW, preferably on its return stroke as indicated in the arrangement of Fig. 3, the fixed pawl FP preventing reverse movement. A return spring (not shown) may be employed to provide the return stroke of the live pawl.

The rotary dial assembly, and consequently the cycle of the step-by-step drum controller serving as a signal circuit controller, are resynchronized cyclically from the resynchronization line RSL from the master controller by means of the local resynchronization relay LRS cooperating with one of the rotary dial switch units LD2- LDS3LDS4 or LD3LDS5LDS6 as more fully described below.

One side of the input of the amplifier LA is connected via wire 33 to the variable frequency common return line VFC, and the other side of the input of this amplifier is connected via wire 34 and the branch wire 61 to the lower contact of each of the cam operated switch contacts 861, SG2 and SY, indicated by the axial broken line as rotated by the step-by-step ratchet drive at the left, for control of the connection of the respective frequency control lines to the input of the amplifier.

The output of the amplifier at one side is connected via wire 35 and relay contacts LRS3LRS4, wire 36 to oneterminal LM2 of the coil of a synchronous motor LS M, and the other side of the output of the amplifier "9 LA -is :connectedvia wire=37 to the other terminal LM3 of this motorcoil.

' Thus the amplifier LA, unler control of the respective frequency lines, repeatsanci amplifies theapplied fre quency to the motor LSM when the 'relay contacts LRS3-LRS4 are closed. 1 elatter contacts are controlled by the-relay LRS, which in turn is controlled by therotary dial operated contacts LDS3-LDS4 in cooperation with the master resynchronization'line REL-RSR for cyclically resynchronizing the rotary dial assembly.

The synchronous motor LSM rotates its output rotor element LM as indicated *by the arrow immediately to the left to rotate the three rotary dials LDl, Li)?- and LD3 shown; schematically asconnected axially with the rotor element LM by the broken line extending downward from LM. The rotary dial LDT. controls the associated switch LDSl, which via wire iii controls the solenoid DStoadvance the drum controllerfrom one step to another in its cycle. .The dial LDZ controls the associated contacts LDSS-LDSd to cooperate with the master controller in resynchronizing the local rotary dial switch assembly with the master cycle unit once per cycle. The dial LD3,similarly controls contacts LDS5-- LDS6.

The rotary dial LDl is provided with several pins DP spaced in desired angular relation around the rotary dial toclose the contacts LDSl momentarily several times during each revolution of the rotary dial so as to operate the step-by-step controller LDC one step at a time for switching the signal circuits. These signal circuits are switched by the drum controller through successive positions to provide the green and'the following yellow periods for street A and then the green and following yellow periods for street'B and to provide a red signal period for street B. overlapping the A green and yellow periods and to provide a red signal period for street A overlapping B green and yellow periods respectively for example.

It. will be understood that this dial LDl is shown in its simplest formwith four pins DP to provide the basic four steps in the cycle comprising the two green signal periods and the two yellow signal periods, but more pins could be provided in the rotary dial and more steps in the cycle of the drum controller so that each green signal period. could overlap more than one position for example as is well known in the art.

The angular distribution of the pins DP around the rotary dial determines the distribution of the total cycle between green and yellow periods for any given. constant speed of rotation of the dial, and determines the length of the green periods for any given setting of the frequency of the respective variable frequency. power circuits. Thus the pins DP may be set for a 50%-50% split of the green periods at the local controllers as shown as abasic split of the individual local cycles subject to variation by the master control of the variable frequency. lines VFLl and VFLZ, which can if desired maintain the same local splitv as established by the settingof the pins in therespective rotary. dials of the respective local. controllers while increasing the green periods. proportionally by decreasing the frequency on both of the variable frequency lines uniformly, with the same frequency on each line, or the split of the cycle may be changed from the master controller by changing the frequencies on the respective lines VFLl and VFLZ by different amounts.

. However, the respective rotary dials LDI of theseveral signal controllers at several traiiic intersections may all have their dial pins DP set for the same basic split of 60%-40% and with the cams'CGl and CGZ in all controllers associated with the same split relation to the variablefrequency lines VPLI and VFLZ for example and with the master control cycle unit MCU having its cyclesplit 60%40% between the two linesV'FLl and VFLZ.

The rotary dial LDZ is provided with one resynchronization pin RP for-deflecting the movable contact LDS3 as'the dialLDZ-rotatesthroughits cycle. The consequent momentary closure of the 'contactLDS3-4 establishes a'connection for the reIay LRS from the resyonchronization line RSL'via wire 33,- the coil of relay LRS, wire"43, contacts LDS3'-4, wire 42 to the resynchronizationro turn linelRSR. Since the 'RSL is supplied with power by the master contacts MSR as shown in Fig. 2 during all but a very small part of the cycle-of the master control unit as indicated by the cam MGR, if the local rotary dial assembly is not in synchronisrn with the master-control unit, the closure of the contacts LDS3-4 by the pin RP will occur while power is on the line RSL and'will consequently energize relay LRSwhich will open the relay contacts LRS3-4 and interrupt the power supply to the motor coil LM2LM3 from the amplifier LA, until the master controlcam MCR opens its contacts MSR went off power on the line R'SL, which will release the relay lJRS and reclose its' contact LRS3 -L'RS4 to restart the motor LSMand restart rotationof "the rotary dial assembly' tomove the pin RP away fromcontacts LDS3-4 and allow themto'reopen' again, so that the rotary'dial unit can continue through its cycle in synchronism with the master control unit.

it will be understood by those skilled in the art that braking means may be employed to stop the rotary. .dial motor LSM quickly so as to avoidcoasting through the resynchronization position, if desired. It will be also understood that the arrangement of the contacts LRS3 LRS lcould-"be reversed so that they would begnormally open and-would beclosed only by energization of relay LRS and such reversed contacts couldthen be connected to close a separate motor brake coil circuit (not shown) to stop the motor inopposition to a normal continuously energized driving coil, in :Which latter alternative arrangement the driving coilptermin'al LMZ' would be directly connected to wire 35 and the reversed contacts LRS3- LRSd would connect the brake coil. directlyacross local power when closed by energization of relay LRS.

It will be appreciated that the startingpoint of the main street or A street green signal for example in relation to the resynchronization point on the other signal controllers along the main street can be determined by the relative positions of the resynchronization pin RP andthe pins DP determining 'thestart of the main street or A green in cooperation with the drum controller. The length of time that the rotary dial travels from the resynchronization pointcontrolled by, pin RP. to the beginning of the next following main street green is usually'referred to as the offset for that controller or signal, and thepin RP is ordinarily located in one or the other green signal parts of the. cycle to avoid having a rotary dial unit dwell in a yellow position until resynchronized if it should be out of step. The corresponding pin R P in the other local controller units for other intersections may be set the same as the pin RP to maintain the several controller units in synchronisrn, or the respectivepins RP in the respective controller units may be set in different relative positions'to the pins DP controlling the beginning of the main street or A green for example to maintain a predetermined phase relation between the controllers so that the beginning of the green at one will. lag behind the beginning of the green at another to allow for travel time along the main street between the controllers and associated signals for example.

For simplicity of illustration in Fig. 3 the normal drum advance contacts D331 and the resynchronization contacts below are shown operated by separate rotary dials rotated in synchronism by the synchronous'mctor LSM. It will be understood that these rotary dial units may be combinedinto one rotary dial unit if desired, with. the pinRP longer than'the pins DP and With the dial contacts arranged. so that the contacts LDSl are operated by the pins DP only an contacts LDS3-4 are operated by the pin RP only, as is common practice in well known types of rotary dial traflic signal controllers,

If control of offsets by the master controller is desired, a second resynchronizing pin RP on an additional rotary dial LD3 with an additional pair of contacts LDS5- LDS6 operated thereby, along with an additional resynchronization line RSR from the master controller can be employed to provide remote selection between two offsets for example, which would be of particular advantage where the overall system is to be operated on a progressive basis with different offsets at the different intersections at one time and on a simultaneous basis with the same offset at all of the intersections at another time for example.

As illustrated in Fig. 3, one contact LDS6 of such additional dial operated resynchronizing contact pair can be connected to wire 43 along with LDS4, and the other contact LDS5 of this added pair connected via Wire 46 to the additional resynchronizing return line RSR, and as shown in Fig. 2 the switch SW interposed between the grounded negative terminal and the line RSR or the added line RSR enables the negative power to be connected selectively to either one or the other of the lines RSR and RSR for selection of one or the other of two sets of offsets as determined by the two resynchronizing pins in each of the local dial assemblies in this alternative arrangement.

As outlined above in connection with the combination of dials LD1 and LDZ, if two resynchronizing circuits and associated dial operated pairs of contacts are provided, the two resynchronizing pins associated therewith could be mounted in different positions on a single dial but differ in length or shape so as to have each resynchronizing contact pair operated only by its associated resynchronizing pin.

It will also be understood that the connections of the wires 38 and 4 2 to the lines RSL and RSR could be interchanged if desired, and in such case if it were desired to add a second resynchronizing circuit the second rotary dial operated resynchronizing contact would be connected to a second line RSL' and a selective switching between RSL and RSL would be provided at the master from the the output of contact MSR instead of on the return line as described above.

It will also be understood that the step-by-step signal circuit drum control unit may be resynchronized cyclically with the rotary dial unit by means of cooperating additional drum and dial pin control. contacts as it well known in the art.

By adjustment of the frequency output of the two cycle generators feeding the respective lines VFLI and VFLZ, the master controller provides the desired control frequencies on these respective lines. These frequencies may be the same at one time and may be different at another time as desired to control the cycle split for the local controllers, the desired frequencies being applied to the respective lines VFLl and VFL2 continuously throughout the cycle of the master controller, and the cams (1G1 and CS2 serving to make the control frequency of line VFLl effective during one green period and the control frequency of VFLZ eh ective during the other green period at the local controller.

It will be appreciated that as pointed out above in connection with the description of resynchronization and the relative positions of the pin RP and the pins DP for example in the rotary dial assembly, the upper three cams for the frequency control circuits and the lower signal cams of one controller of a series along a street for example may have one phase relationship to the resynchronizing point of the master cycle and those of an other controller may have another phase relationship so that at any one time as for example at any particular point in. the master control cycle, difierent local controllers may have their respective amplifiers LA operated by different frequency lines, under the control of the upper cam group of each local controller but the frequency of either line is available continuously for selection by 111 a onta t of the respective local controllers so that the local controllers may have their green periods in different phase relationship to each other but have the main street or A street green periods controlled from one frequency line and the cross street or B street green periods for example controlled by the other frequency line. In this connection it will be appreciated that in grid systems of signals or other situations in which the cross street at a particular intersection might require a longer green period than the main street in contrast to other intersections in a series or group, the circuits at this particular local controller could be interchanged with respect to the cams CGIl, CG2 of this controller or the relationship of these cams C61 and C62 to the cams CAG and CBG in this particular controller could be changed so that the variable frequency line VFLI would control the cross street or B street green and the variable frequency line VFLZ would control the main street or A street green.

Considering the several frequency control circuits in the local controller in more detail it will be noted that one side of the amplifier input is connected continuously to the variable frequency common return line VFC by wire 33, and the other side of the amplifier input at wire 34 is connected either directly or by way of the branch wire 61 to the lower contact of each of the contact pairs SGT, 8G2 and SY controlled by the cams CGl, CGZ and CY respectively. The upper contact of SGl is connected via wire 51 to the variable frequency line VFLl. The upper contact of SG2 is connected via wire 53 to the second frequency line VFL2. The upper contact of SY is connected via wire 5'7 to one side of the output winding T2 of the transformer designated LFF providing fixed frequency power for application to the amplifier LA during the yellow or trafiic clearance periods of the cycle under control of cam CY. The other side of the winding T2 is connected via wire 58 to the variable frequency comm-on return line VFC. The input winding T1 of the transformer LFF is connected to local fixed frequency power such as the usual 60 cycle alternating current supply commonly available, indicated by the circles marked plus and minus.

The transformer LFF serves as a voltage matching and isfilating transformer where it is desired to use a different voltage such as a lower voltage for example for the input to the amplifier LA than is available on the ordinary local power supply, or where it is desired to maintain the several frequency supply lines and the amplifier input isolated from ground.

It will be observed that in this embodiment of the invention the pattern of the cam CGl corresponds with the cam CAG controlling the A green signal and the cam CGZ has the same pattern as the cam CBG controlling the B green signal. Thus the variable frequency line VFLI is connected only in the A green part of the local signal cyle to control the synchronous motor LSM through the amplifier LA and thus to control the rate of rotation of the rotary dial assembly and consequently the length of the A green signal period for any predetermined setting of the pins DP on the rotary dial LD1. Similarly the cam CGZ makes only the second variable frequency line VFLZ effective during the B green part of the signal cycle to control the speed of rotation of the rotary dial assembly and thus control the length of the latter green period for any setting of the pins DP on the rotary dial.

The cam CY has a pattern combining the contact operating periods of the cams CAY and CBY for the yellow or clearance signals of the respective streets following the respective green signal periods. Thus the cam CY closed its contacts SY in both the A yellow and B yellow signal periods of the signal cycle to make effective the local. fixed frequency power supply for control of the synchronous motor LSM and thus to controlthe speed of rotation of the rotary dial assembly to determine the lengths of these yellow periods for any setting of the pins DP in the rotary dial.

avenue It will be noted" that the length of'the yellow-periods maybet set'for .a longer'or shorter timeperiod at all of J the local controllers as desired by increasing or decreasing the angular spacing of the pins DP determining the stepping of the. drum controlleriuto and out of the re spective yellow signal positions. A typical setting widely used at the present time in traiiic signal systems is about 3 seconds for each yellow signal period or a total of 6 seconds for twosuchperiods in a signal cycle for example. Where the individual rotary dial units in the respective local controllersare set for this time period the cams MCll and MCZ in the master controller are set to give a corresponding total period ofabout 6seconds of operationof the master synchronous motorMSM on the master fixed frequency power supply from transformer FF which may conveniently correspond with the local fixed frequency power supply. If the yellow signal periods as set by the rotary dial units in the-local signal controllers are increased or decreased, the corresponding brief open period between the projecting cam lobes on themaster cams MCI and MC2 and the brief overlapping period of these lobes are preferably increased or decreased accordingly so that the master controller will be operated on fixed frequency power for substantially the same length of time in each cycle as thelocal controllers.

Since the "fixedfrequency may conveniently be near the middle of the range of variation of the variable frequency lines however it will be appreciated that the average of the two variable frequencies in effect atany time-may be' greater than the fixed frequency, or the average speed of rotation of the master controller unit MCU during the variable frequency controlled parts of the cycle maybe greater than during "the fixed frequency parts'of the cycle, or these conditions might be reversed depending upon the variable frequencies in effect on the two variable frequency lines in any particular cycle.

Thus it .is possible for any shortening of the yellow periods of. any particular local controller-by its rotary dial setting to cause either an increase or 'a decrease in the time length of the total cycle required to reach its resynchronization point depending upon the relations of the fixed frequency to' the variable frequencies in effect. Similarly the lengthening of the yellow periods by the rotary dialsettings at aparticular local controller may also either lengthen or shorten the time required for the local controller to complete its cycle from the point of its release from the master at one local resynchronization point to the next.

In order to allow for some slight variations 'inthe local controllers units with respect to adjustment of the yellow periods or other factors affecting the average speed of rotation of the local controller through its cycle, the master controller cycle unit MCU is preferably arranged to have a slightly longer time cycle than the local controllersso that the local controllers will dwell briefly in each cycle on reaching the local resynchronization point until released by the master control unit or master cycle unit. This may be accomplished by heaving a slightly greater gear reduction in the gear train commonly provided between the master synchronous motor MSM and the cyclic switch unit rotated therebyincluding the cams MCI, MCZ and MCR'for example. The cycle length of master control unit MCU is preferably made suificiently long to allow the slowest local controller to complete its cycle witha slight margin.

It will be noted that two different forms for means of selectively connecting one or another of the several frequency sources to the amplifier for control of the cycle are shown in the master controller in Fig. 2 and in' the local controller in Fig. 3. Thus in Fig. 2 the switching of the amplifier circuit between the several frequency supply lines is shown as accomplished by contacts controlled by relays which in turn are controlled by cam operated contacts; whereas in Fig. 3 the switching of the amplifier circuit between the several frequency supply-circuits is 1d accomplished by direct' opera'tion of cam operated'switches without any intervening relays.

It will be appreciated by thoserskilledin' the art-that adirectcam contact method-of-control similar to" that illustrated in Fig. 3 couldbe" appliedto the master-controller in place of the combination of cam contact" and relay control illustrated in Fig. 2, andthat relay could be interposed in the control circuitsin Fig. 31in the local controller similar to the'arrangement illustrated in Fig. 2 for the master controller; with the cams in each case having the appropriate patternstfor-tconnection"of VFLl in'one greenperiodaudVFLZ in the other greenperiod and the local fixed frequency winding T2 in both 'yellow periods'at the local controlleryandfor connection of VFLl during one part of the cycle say 46%, for example, andconnection of'line VFLZ'foranother part of the. cycle say an0ther46%, for example, and-connection of fixed frequency line winding W2" for thepbalance ofthe cycle say 8% for example in the master controller, alongthe lines indicated in theseiigures =and previouslydescribed.

Thusgrelays of the same typeand contact .and circuit arrangement'as in R1. and R2 in'Fig. 2 could be substituted. in control ofth'e circuit of amplifier'LA, the relays to becontrolle'd by cams CGI and C62 in the local controllerand their associatedcontacts SGI and SGZ; and correspondingly three cams "and associated contacts andcircuits as inxthe case of thecams CGL (3G2 and CY in Fig. 3 could be substituted for. the cams MCI and MCZ. and associated cam contacts and. relays and I asso- 'ciated relay contacts inFig. 2 of the master controllenbut with the contact closure periodslof CGI and C62 enlarged to. approximately 46%. of. the cycle where-[continuously driven as illustrated inFig. 2 form or cycle. unit and..with the cam CY having its contact, closure. periods. diminished to cover approximately the 8% balance of .the. cycle .where used in the continuously rotary drivearrangement. of the master. controller of Fig. .2. It will'.be, appreciated. that where the cams..are used to control the connectionof the respective frequency supply circuits directly. through cam contacts insteadof intervening r'elays, any overlap: ping of theseseveral cams shouldbe-a voidedto. eliminate the possibility of ,connecting two conflicting. frequency supply circuits to theamplifier at. the same. time. Other possible relay or.,cam arrangementwill suggest.themselves to thosei skilled in .the art in..view. of ,the. .several alternative arrangmentsoutlined above and. the different arrangements illustrated in,.Figs.; 2..and :3.

It will be appreciated that the green .signalv display period may overlap .the yellow signal displayperiod in some traffic control systems. by, overlappingrcamarrangements. as .is well. known. .in the :art,v and .the green .and yellow ove'rlapperiodwould then be considered .the clearance period andlthe greenalone would be considered thefigo. or .true. green period.

It will be understood that the frequency ofthe variable frequency power. is variablein ..the..sense that it may beadjusted as. desired for. remote control. of the green signalparts of the cycle. for example, but such frequency may remain set at; some. desired constant value for a considerableperiod of time, such as. for oneeor several signal cycles for exampleand .thenmay .be changed to another constant value for a further period of time, but the. frequency change on either of thetvariable. frequency power circuits may also. be made at the master ifdesired at. anytime during. the master. cycle.

'Thefact that the .split of the. cycle throughout all the.local..controllers.ofithe system can be changed at any timeuby. the master controllerwithout regardto, the particular signal display .at any of the local controllers is .adistinct advantage ofthe. system :according to "the present .inventionin contrast tto prior. systems in which switching. of local controllers from one rotarydial ass.em-. bly .to another is employedwithcomplex auxiliary apparatus at each local .controllertoassure .that therewill not be a suddenreversalor other .unexpected change in signal'display in such switching of rotary dials.

Although a number of alternateforms or arrangements of the apparatus according to the invention have been pointed out above, it will be obvious to those skilled in the art that other modifications of the apparatus or the arrangement or character of its parts may be made without departing from the spirit of the invention within the scope of the claims.

Weclaim:

1. A traffic control system for interfering trafiic lanes including right-of-way signal circuits for the respective lanes, cyclic switching means for operating one of said right-of-way signal circuits in one part of its cycle and for operating another of said right-of-way signal circuits during another part of its cycle, synchronous motordrive means for operating said cyclic switching means through its cycle, two remotely controlled variable frequency supply circuit means for operating said synchronous motor at varying speed in accordance with varying frequency on whichever of said circuit means is connected thereto, each of said variable frequency circuit means having its frequency variable separately from the other such circuit means, and further switch means cooperating with said cyclic switching means for connecting one of said variable frequency circuit means to operate said synchronous motor drive means during one right-of-way signal circuit operating part of said cycle and for connecting the other of said variable frequency circuit means to operate said synchronous motor driving means during the other rightof-way signal circuit operating part of such cycle.

2. Trafiic signal control apparatus including right-ofway signal circuits for each of two interfering trafiic lanes, a cyclic circuit controller having a cycle of operation for one of the right-of-way signal circuits followed by the other of said right-of-way signal circuits when operating, a frequency responsive driving means for said cyclic controller for operating the controller at varying time rates in response to variations in frequency, two remotely controlled independently variable frequency sources for said driving means, and switch means controlled by said cyclic controller for connecting said driving means to one of said variable frequency sources during one part of said cycle for control of one of said right-of-way signal circuits and for connecting said driving means to said other variable frequency source during another part of said cycle for control of said other right-of-way signal circuit.

3. Trafiic signal control apparatus including two sets of signal circuits for go" signals and clearance signals for two interfering traflic lanes, a cyclic circuit controller having a cycle of operation for the go and clearance signal circuits of one set followed by the go and clearance signal circuits for the other set when operating, a frequency responsive driving means for said cyclic controller for operating the latter at variable time rates in response to variations in frequency,two separately variable frequency sources for said driving means, a fixed frequency source for said driving means, and switch means controlled by said cyclic controller for operatively connecting said driving means to the respective variable frequency sources during the respective go signal parts of the cycle for individual control of the time length of the respective fgo signal parts of the cycle and for connecting said driving means to said fixed frequency source during the clearance signal parts of the cycle.

4. In a tratfic signal control apparatus, a signal circuit controller having a cycle of operation, a frequency responsive driving means for said controller, two variable frequency power sources having separately variable frequencies, and switch means operated by said controller in its cycle to operatively connect one of said variable frequency power sources to said driving means during one part of the cycle and to connect the other of said variable frequency power sources to said driving means during another part of the cycle for individual control of the respective parts of the cycle by adjustment of the frequencies of the respective variable frequency power sources.

5. In a traffic signal control system, a signal circuit 16 1 controller having a cycle of operation, a frequency responsive driving means for said controller, two variable frequency power circuits having individually variable frequencies, switch means operated by said controller in its cycle to connect one of said variable frequency power circuits to said driving means during one part of the cycle and to connect said other variable frequency power circuit to said driving means during another part of the cycle, and remote control means for varying the frequencies of the respective variable frequency power circuits for remote control of the length and relative proportions of the two parts of the cycle.

6. In a trafiic control system, a fixed frequency power supply, two variable frequency power supplies having individually adjustable frequencies, a traffic signal controller having a cycle of positions through which it is adapted to be operated for control of the tralfic signal at variable time rates in accordance with variable frequency input to the controller, said cycle including a position for operating a first go signal, a following position for operating a first clearance signal, a following position for operating a second go signal and a following position for operating a second clearance signal, and means controlled by said controller in its cycle of operation to connect said fixed frequency power supply as input to said controller during the clearance signal operating positons of said cycle, and means controlled by said controller in its cycle of operation to connect one of said variable frequency power supplies as input to said controller during one of the go signal operating positions of said cycle and to connect the other of said variable frequency power supplies as input to said controller during the other go signal operating position of said cycle whereby the respective go signal operating periods of the cycle may be individually controlled by adjustment of the respective variable frequency power supplies.

7. In a traffic control system, two separately variable frequency power sources, a traffic signal controller having a synchronous motor and having a cycle of positions through which it is adapted to be operated by said motor for control of a traffic signal at variable speeds substantially proportional to the frequency input to the said motor, and means controlled by said controller in its cycle of operation to connect one of said variable frequency sources as input to said motor during one part of said cycle and to connect the other of said variable frequency power sources as input to said motor during another part of the said cycle.

8. In a trafiic control system, a master control unit having two variable frequency power generators, means for varying the frequency output of each of said generators individually, a cyclic controller operable at variable time rates through its cycle in accordance with variations of frequency applied to operate it, and switch means controlled by said cyclic controller in its cycle to apply the variable frequency output of one of said generators to operate said controller during one part of its cycle and to apply the variable frequency output of said other generator to operate said controller during another part of its cycle; a local signal controller having a cycle of operation for trafiic signal control, a frequency responsive driving means for said local controller, and switch means operated by said local controller in its cycle to operatively connect the variable frequency power from one of said generators of said master control unit to said local driving means during one part of said last named cycle and to operatively connect the variable frequency power from said other generator of said master control unit to said driving means during another part of said last named cycle the two said parts of said last named cycle corresponding in relative proportions to the two parts of the first named cycle; and means for cyclically resynchronizing the local. controller cycle with the master controller cycle.

9 In a trafiic control system, a master controller having two variable frequency power generators, and means for individually varyin the frequencies of the outi put of the respective generators, a fixed frequency power source, a cyclic controller operable at variable time rates through its cycle in accordance with variations of frequency applied to operate it, and switch means controlled by said cyclic controller in its cycle to apply the fixed frequency power from said fixed frequency power source to operate said controller through one part of its cycle and to apply the variable frequency output of one of said generators to operate said controller during another part of its cycle and to apply the variable frequency output of the other said generator to operate said controller during the remaining part of its cycle; a local signal controller having a cycle of operation for trafiic signal control, a frequency responsive driving means for said local controller, and switch means operated by said local controller in its cycle to operatively connect a corresponding fixed frequency source to said local driving means during a first part of said last named cycle corresponding to the first part of the master controller cycle, and further switch means operated by said local controller in its cycle to connect the respective variable frequencies from the respective two generators of said master controller to said driving means during two respective additional parts of said last named cycle for individual control of the respective last named parts of the cycle by variation of the respective frequencies of the respective generators, said local controller being operated by its frequency responsive driving means through its cycle in a slightly shorter time than the said master cyclic controller; and means controller cooperatively by said master controller and said local controller for cyclically resynchronizing the local controller cycle with the master controller cycle by causing the local controller to dwell in part of each cycle until the master controller reaches the corresponding point in its cycle.

10. In a trafl'lc control system of the master-local type, a master controller having two variable frequency power generators, means for varying individually the frequency of the respective generators, a fixed frequency power source, a cyclic controller operable at variable time rates through its cycle in accordance with variations in frequency applied tooperate it, and switch means controlled by said cyclic controller in its cycle to apply the variable frequency output of one of said generators to operate such controller during one part of its cycle and to apply the variable frequency output of the other of said generators during another part of its cycle, the two parts of the cycle comprising a major part of the total cycle, and to apply the fixed frequency power to operate said controller through a minor part of its cycle; a local signal controller having a cycle of operation for tratlic signal control including a phase for trafic right-of-way followed by trafiic clearance and a second phase for other tratfic right-of-way followed by other trafiic clearance, a frequency responsive driving means for said local con troller, and switch means operated by said local controller in its cycle to connect the respective variable frequency outputs of the respective generators from the Inaster controller to said local driving means during the respective right-ofiway parts of said last named cycle for individual control of the respective right-of-Way parts of the cycle by adjustment of the frequencies of the respective generators at the master controller and to connect a fixed frequency source corresponding to the first named fixed frequency source to said local driving means during the trafiic clearance parts of said last named, cycle, the first two parts comprising the major part of the first named cyclic controller cycle corresponding with the right-of-way parts of the local controller cycle and the minor part of the first named cyclic controller cycle; means including other switch means controlled by the first named cyclic controller. in the master controller and further switch means operated by said local controller tively connecting the respective variable and fixed frequency power sources to said controllermeans in the respective parts of its cycle.

12. A trafiic signal controller including output circuits for a first go signal, a first clearance signal, a second go" signal and a second clearance signal, a cyclic switch unit having a cycle of operation for the several signal circuits in sequence respectively when operating, a frequency responsive driving means for operating said cyclic switch unit at variable time rates in response to variations in the frequency respectively, two variable frequency input circuits for said driving means, switch means operated by said cyclic switch unit in the first go signal operating part of the cycle for connecting one of said variable frequency circuits to said driving means, and furtherswitch means operated by said cyclic switch unit in the second go signal part of said cycle for connecting the other of said variable frequency circuits to said driving means for individual control of the respective go signal periods by variation of the frequencies of the respective variable frequency circuits, and additional means operated by said cyclic switch unit in both of the clearance periods of said cycles to operate said driving means in said clearance periods.

13. In a traffic control system, a first variable frequency source, a second variable frequency source, a sigadjustable angular relationship for determining the proportions of its total cycle allocated to the respective rightof-Way periods for any predetermined speed of rotation of said rotary dial unit, a synchronous motor for driving said rotary dial unit at a speed substantially proportional to the frequency input thereto, switch means controlled by said signal circuit controller for connecting said first variable frequency source to said synchronous motor in one of said right-of-way signal positions and for connecting said second variable frequency source to said synchronous motor in another of said right-of-way signal positions, and remote control means for varying the frequencies of the respective frequency sources individually to vary the speed of said synchronous motor to vary the lengths of the respective right-of-way periods individually for varying the proportions of the total cycle allocated to the respective right-of-way periods.

14. In a traffic control system of the master-local type, a first variable frequency supply circuit; a second variable frequency supply circuit; a plurality of local signal circuit controllers each having a cycle of operating positions including a plurality of right-of-way signal circuit positions, a rotary dial cycledistribution unit having actuating elements arranged in adjustable angular relationship for operating said signal circuit controller through its cycle of positions and determining the proportions of its total cycle allocated to the respective right-of-way periods for any predetermined speed of rotation of said rotary dial unit, a synchronous motor for driving said rotary dial unit at a speed substantially proportional to the frequency input thereto, switch means controlled by said signal circuit controller for connecting said first frequency supply circuit to said synchronous motor in one of said right-of-way signal positions and for connecting said second frequency supply circuit to said synchronous motor in another of said right-of-way signal positions, and a further actuating element and associated switch means in said rotary dial unit for interrupting. the rotation thereof at any desired part of its cycle of operation in. desired relationship to one of the respective rightaof-way periods, all associated with and individual. to each local signal circuit controller; a master controller including means for varying the frequencies of the respective variable frequency supply circuitsindividually, a master cyclic switch unit operable through its cycle at a speed substantially proportional to the frequency input thereto and havingswitch: means for connecting the input of the cyclic switch unit to said first frequency supply circuit during one part of its cycle and to the second frequency supply circuit during the second part of its cycle, and further switch means operated by said cyclic switch unit in a predetermined part of the cycle of the latter for restarting of. the several local rotary dial units in synchronism cyclically with the cyclic switch unit in the master controller.

15-. In a traffic control system of'the" master-local type, a first variable frequency supply circuit; a second variable, frequency supply circuit, a fixed frequency supply circuit, a plurality of local signal circuit controllers each having a cycle of operating positions including v a plurality of right-of way signal circuit operating positions and following clearance signal circuit operating positions, a rotary dial cycle distribution unit individual to each of said controllers and having actuating elements arranged in adjustable angular relationship for operating its associated signal circuit controller through its cycle of positions and determining the proportion of its total cycle allocated to the respective right-of-way periods and clearance periods for any predetermined speed of said rotary dial unit, a synchronous motor individual to each said rotary dial unit for driving its associated rotary dial unit at a speed substantially proportional to the frequency input thereto, switching means individual: to and controlled by each said signal circuit controller to connect the said synchronous motor of its associated rotary dial unit to said first variable frequency supply circuit in one of said right of-way signal positions and to said second variable frequency supply circuit in the second of said right-ofway signal positions and for connecting said synchronous motor to said fixed frequency source in said clearance positions, and a further actuating element and; associated switch means individual to each said rotary dial unit for interrupting the rotation thereof at any desired part of its cycle of operation in desired relationship to one of the respective right-of-wayperiods, a master controller including means for varying separately the frequencies of the respective variable frequency supply circuits and maintaining power of the selected: frequencies continuously applied to the two variable frequency lines. respectively, a master cyclic switch unit operable through its' cycle at a speed substantially proportional to the frequency input thereto and including switch means for connecting the input of the cyclic switch unit to a frequency source of substantially the same frequency as said fixed frequency supply circuit for a part of its cycle approximating the total time of said clearance periods and for connecting the input of the cyclic switch unit to said first variable frequency supply circuit during another part of the cyclic switch unit and for connecting the input of the cyclic switch unit to the second variable frequency supply circuit during a still further part of the latter cycle, the latter two parts of such cycle together with the first mentioned part of such cycle comprising the. full cycle of the said cyclic switch unit, and further switch means operated by said master cyclic switch unit in a predetermined part of the cycle of thelatter for restarting rotation of the several local rotary dial units in synchronisrn I6. In a traffic control system of the master-local control type, a first variable. frequency supply circuit;

a second variable frequency supply circuit; a third frequency supply circuit; a resynchronizing; circuit; a plurality of local signal circuit controllers each. having a cycle of operating positions including a plurality of positions for operating, right-of-way signal circuits and following positions for operating clearance signal circuits, each local signal circuit controller having associated therewith a rotary dial cycle distribution unit having, actuating elements arranged in adjustable angular relationship for operating said signal. circuit controller throughits cycle of positions and determining the proportions of its total cycle allocated. to the respective right-of-way positions and clearance positions for any predetermined speed of rotation of said rotary dial unit, a, synchronous motor for driving said rotary dial unit at a speed substantially proportional to the frequency input thereto, a cam operated switch controlled by said signal circuit controller for connecting said first frequency supply circuit to said synchronous motor the first of said. right-of-way signal positions, another cam operated switch, for connecting said second frequency supply circuit to said synchronous motor in said second right-of-way signal posi tion, and a third cam operated switch means for con-- meeting said third frequency supply circuit to said synchronous motor in said clearance positions, and a further actuating element and associated switch means in said rotary dial unit for interrupting the rotation thereof at any desired part of its cycle of operation. in desired relationship to, one of the respective right-of-way periods under control of said resynchronizing. circuit, all individual to each local signal circuit controller; a master controller including means for varying separately the frequencies, of the first and second frequency supply circuits and maintaining the selected frequencies continuously applied to the respective first and second frequency supply circuits, a master cyclic switch unit operable through its cycle at a speed substantially proportional to the frequency input thereto and having a setof' cams and associated switch means controlled thereby for connecting the inputof the cyclic switch unit to a frequency source of substantially the same frequency as said third frequency supply for a part of its cycle ap' proximating the total time of the said clearance periods and for connecting the input of the cyclic switch unit to said first frequency supply circuit during another part of its cycle approximating the part of the cycle of the local controllers allocated to the first right-of-way period and for connecting the input of the; said cyclic switch unit to said second frequency supply circuit during a further part of its cycle corresponding to the part-of thecycle of the local controllers allocated tothe second right-owayperiod, and further switch means operated by said cyclic switch unit in said master controller in a predetermined part of the cycle of the latter for control of said resynchronizing circuit for controlling, the several local rotary dial units to restartsaid several local rotary dial units in synchronism cyclically with the cyclic switch unit of the. master controller.

17. A traffic signal controller including output circuits for a first go signal, a first clearance signal, a second go signal, and a second clearance signal, a cyclic circuit controller having a cycle of operation for the several signal circuits in sequence respectively when operating, a rotary dial cycle distribution unit for operat; ing said cycle controller through its cycle of positions and having actuating elements therefor arranged in adjustable, angular relationship for determining the proportions of its total cycle allocated to the respective go." signal positionsand, clearance periods. for any predetermined speed, of rotation of said rotary dial unit, a syn-- chronous motor for driving said rotary dial unit at a speed substantially proportional to the frequency input thereto, a first frequency supply circuit, a second frequency supply circuit, and a third frequency supply circuit, switch means controlled by said cyclic circuit controller for connecting said synchronous motor to be operated by said first frequency circuit in the first g0 signal part of said cycle and to said second frequency circuit in the second go signal part of said cycle and to said third frequency circuit in the said clearance sig nal parts of said cycle.

18. In a traffic control system, an apparatus as in claim 17 and remote control means for selectively varying the frequency individually of certain of said frequency circuits to control the proportions of the cycle devoted to the respective go signals.

19. An apparatus as in claim 18 and including a master cyclic switch unit, a synchronous motor for driving said master cyclic switch unit through its cycle, switch means controlled by said master cyclic switch unit for selectively connecting the synchronous motor associated with said mastercyclic switch unit to the respective frequency circuits during the respective parts of its cycle corresponding to the respective go signal and clearance signal parts of the first named signal cycle, to enable the master control cycle to approximate the said signal cycle for Wide variations of frequency selected for the respective several frequency circuits and switch means controlled by said master cyclic switch unit and switch means controlled by said rotary dial unit cooperating for resynchrcnizing said rotary dial unit with said master cyclic switch unit cyclically.

References Cited in the file of this patent UNITED STATES PATENTS

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