US3056107A - Traffic actuated control apparatus - Google Patents

Description

Sept. 25, 1962 J. L. BARKER 3,056,107

' TRAFFIC ACTUATED CONTROL APPARATUS Filed June 20, 1958 2 Sheets-Sheet 1 CONTROLLER A STREET"A" STREET "B" STREET "0" FIG. I

CAM SEQUENCE CHART INVENTOR. JOHN L. BARKER 622mm lum ATTORNEY Sept. 25, 1962 J. L. BARKER TRAFFIC ACTUATED CONTROL APPARATUS 2 Sheets-Sheet 2 INVENTOR. JOHN L. BARKER Filed June 20, 1958 ATTORNEY United States ice 3,056,107 TRAFFIC ACTUATED CONTROL APPARATUS John L. Barker, Nor-walk, Conrn, assignor, by mesne assignments, to Laboratory For Electronics, Inc., Boston, Mass, a corporation of Delaware Filed June 20, 1958, Ser. No. 743,394 Claims. (Cl. 340-36) This invention relates to traffic actuated control apparatus suitable for traffic signal control of three individual traflic flows at the intersection of a main street and two or more side streets, or at offset intersections where two side streets individually intersect the main street some distance apart, for example, and where it may be desired to alocate right-of-way to the several trafiic flows in a sequence of phases that may be described as A-BAC, where A represents the main street phase, B represents one side street phase and C represents the other side street phase, when both phase B and phase C are called for by traffic actuation on the respective side streets, or a sequence of AB- A-B when there are multiple actuations by phase B trafiic and an absence of actuations by phase C trafiic, or a sequence of AC AC when there are multiple actuations by phase C trafiic and an absence of actuations by phase B trafiic, with return to A at the end of each of such sequences.

British Patent 416,588, accepted September 18, 1934, discloses trafiic control apparatus producing such sequences, but with certain limitations, particularly in the sequences AB-A-B and AC-A-C as more fully pointed out below.

This British patent shows a three phase traflic signal controller providing for traflic actuation on all three phases, but also providing for return of the right-of-way to a particular phase such as phase A for example in absence of traific, if desired.

The British patent has a controller employing a cam shaft having individual steps in its cycle for green and yellow (or amber) periods for the four stages of the complete cycle ABAC and thus in skipping one phase in absence of traflic there, as in skipping phase C in the AB-AB sequence for example, its controller must step through the several positions of C and the following A, and although it does so by stepping rapidly with reduced timing while the signals remain red, this introduces delay into the operation of the system, which is avoided in the improved controller according to the present invention.

Thus in the present improved controller a two phase cam cycle is made to provide for the four stage A-B A-C sequence by two successive cycles of operation and the cam positions intervening between those of A serve either for B or C, as conditions require, but in any event it is assured that the phases B and C will be served in order if there is traffic actuation on both. This is accomplished by predetermining whether the common cam shaft positions will next serve B or C in accordance with the condition of a relay circuit which in effect remembers which was last served, but which permits without delay an A-BA-B sequence in case of traflic actuation on B alone and an ACA-C sequence for trafiic actuation on C alone. The right-ofway also returns to A at the end of each of such sequences to be prepared for the next transfer to B or C as the case may be.

The preferred embodiment of the present invention is a semi-actuated three phase tratfic control apparatus or traffic signal controller which automatically returns rightof-way to phase A, the non-actuated phase, for at least a minimum period, after each side street phase is accorded right-of-way through trafiic actuation, and in which the determination as to which one of the side street phases is next to be served in a part of the cycle potentially common to both, is made through trafiic actuation and the cooperation of certain relays as hereinafter described.

It is a general object of the invention to provide an improved traific actuated control apparatus or trafiic signal controller for normally according right-of-way to one major traflic roadway in absence of traffic on two minor traffic roadways, for according right-of-way to either one of the minor roadways alone or each in succession in response to trafiic actuation on either one or both respectively, and for according right-of-way to the major roadway after each accord of right-of-way to either minor roadway before reaccord of right-of-way to the same or to the other minor roadway.

It is also an object of the invention to provide an improved trafiic actuated control apparatus or controller for traffic signal control of intersecting traific in a major road and two minor roads and having a basic cycle of operation providing for accord of right-of-way to the major road and then for potential accord of right-of-Way to either one of the minor roads and then return accord of right-of-way to the main road again, and in whichthe minor road to which right-of-way is to be accorded, in such potential right of way part of the cycle in response to tratfic actuation, is predetermined in each cycle in accordance with traflic actuation on the respective minor roads in combination with means for remembering Other objects will become apparent during a reading of the description below with reference to the accompanying drawings.

FIG. 1 is a schematic plan view of an intersection showing a main street and two side streets and the location of traific detectors, signals and the traflic controller controlling the intersection traffic.

FIG. 2 is a schematic circuit diagram of the preferred embodiment of the present invention.

FIG. 3 is a cam sequence chart showing each of the six positions of the cam shaft of the controller illustrated in FIG. 2 with indications of the closed cam contacts in each of the six respective positions.

FIG. 1 illustrates, in plan view, an intersection of three streets, Street A, Street B .and Street C, for example, each street being controlled by signal lights, represented by circles located in the respective streets as described below, which signal lights are controlled by a traflic controller, of the type described below, represented by a For simplicity in FIG. 1 the connections are shownin single line form to one side of the signals and detectors, but it will be understood that return lines would be connected to the other sides of the signals and detectors, as shown in FIG. 2.

Vehicle trafiic along Street A is controlled by trafiic signal lights represented by circles labeled AR and AR, red signals, AY and AY', yellow signals, and AG and AG, green signals. These signals are controlled by the controller CX to which they are connected. It will be assumed for the purpose of illustration that Street A is the main street or artery for vehicle traflic.

The vehicle traflic approaching the intersection along Street B is controlled by signal lights, represented by circles labeled BR, a red signal, BY, a yellow signal, and BG, a green signal. These signals are also connected and controlled by the controller CX. A rectangle VB, representing a vehicle detector, is illustrated in the Street B located in the lane that is traveled by vehicle trafiic approaching the intersection.

The vehicle detector may be any one of the well known vehicle detectors, whether pressure or sound sensitive, magnetic or light sensitive, mechanical, electrical or electronic, located above, in or under the surface of the roadway, designed to close a set of contacts. For convenience it will be assumed that the vehicle detector VB is a pressure sensitive type detector located in the surface of the roadway designed to close a set of contacts when pressure is applied to the same.

The vehicle detector VB is connected to the controller CX to which the presence of a vehicle will be indicated when a vehicle approaching the intersection along Street B crosses over the vehicle detector. Such indication shall hereinafter be referred to as a call.

Vehicle traffic approaching the intersection along Street C is controlled by signal lights represented by circles labeled CR, a red signal, CY, a yellow signal, and CG, a green signal. These signals are connected to the controller CX by which they are controlled.

A vehicle detector represented by a rectangle labeled VC similar in type to vehicle detector VB, i connected to the controller CX to which the vehicle detector VC sends calls indicating the presence of vehicles approaching the intersection on Street C.

It should be noted that although the signal lights are illustrated in the roadway that they control, it is assumed that such signals would be located overhead. It is obvious that the signals may be located at other convenient locations at the intersection so that the signals would be visible to the vehicle traffic the signals c ntrol.

The location of the controller is of relatively little consequence. It may be located at any convenient location at or near the controlled intersection Where electrical power, to operate the controller, is available.

Referring to FIG. 2 in more detail, a circuit diagram of the preferred form of the controller is illustrated. The relays AS, BS, BL, CL, PB, PC, LB, LC, BD and CD are illustrated as deenergized. The solenoid SOL is also illustrated as deenergized. The contacts of the several relays are arranged above and/or below the respective relays, as the case may be, with a vertical broken line extending from the relay through the moving part of the contacts controlled by the relay.

Several cam contacts, indicated by a numeral with the letter C preceding the numeral, are illustrated open while others are illustrated closed. It will be understood from the cam contact chart in FIG. 3 that in various positions of the cam shaft, certain of the cam contacts will be open while other cam contacts will be closed, according to what position, 1 through 6, the cam shaft is then in. In the lower part of the diagram are nine circles, representing nine signal lights, three red, three yellow and three green, one set, consisting of three difierent colors, employed to control three phases of traffic. A switch S1, illustrated as closed, is shown inside a broken line box. The switch may be external to the circuit, or may be omitted from the circuit. If the switch is omitted the line 70 in which the switch is located would be connected directly to ground, if the switch is in the circuit but external to the circuit the switch when closed would connect the lead 70 of the controller to a common ground. The use of the switch is explained below.

The controller is arranged for operation by 120 volt alternating current, for example, represented by a plus in a circle for positive power and a minus in a circle for negative power and common ground. This AC. power is employed to energize some of the relays and all of the signal lights. It should be understood that the signal lights are actually external to the controller but are here represented as internal parts for convenience of illustration.

Direct current power on the order of 425 volts, for example, represented by a plus in a square, applied to a potential divider, PDX, is employed to charge the timing capacitors KA and KB which capacitors are associated with flasher tubes FA and PB respectively. It should be understood that although the timing method herein illustrated is the flasher tube-capacitor combination, such illustration is not to be construed as restricting the controller to include such timing method as other timing methods, well known to those skilled in the art, may be employed in lieu of the method herein illustrated, with similar effect.

An alternating current supply, on the order of 12 volts, for example, represented by plus in a circle, in a square, is employed in the detector circuits which include relays BD and CD, contacts VB and VC, several relay contacts and several cam contacts, all of which will be described in detail hereinafter. The contact VB is similar to and represents the vehicle detector VB of FIG. 1 while the contact VC of FIG. 2 is similar to and represents the vehicle detector VC of FIG. 1.

The cam shaft employed herein is a six position cam shaft which is partially rotated of a complete rotation each time the solenoid SOL is energized and subsequently deenergized. Upon being energized the solenoid SOL notches a ratchet wheel (not shown) and, upon deenergization, the ratchet wheel is partially rotated, approximately of a complete rotation, for example, which in turn partially rotates the cam shaft. It should be understood that the cam shaft can have multiples of six positions per revolution, if desired.

Referring momentarily to FIG. 3, a cam shaft chart is presented in graph form. On the left of the chart are numbers 1 through 6 which represent the six positions of the cam shaft. It should be understood that position 1 will immediately follow position 6 in sequence of rotation. Across the top of the chart, each in its own box, are the letters C followed by a numeral. These identifying figures in FIG. 3 are similar to identical identifying figures found in the circuit diagram in FIG. 2 and represent the corresponding cam contacts illustrated in FIG. 2 identically identified in both figures. Below each of the identifying figures are six squares representing the six positions of the cam shaft, 1 through 6, as indicated on the left of the chart. The X in a box or boxes below the identifying figure indicates that the cam contact identified above is closed when the cam shaft is in that position identified on the left.

Referring again to FIG. 2, the cam contacts are presented with cam contacts C13, C24, C27, C31 and C40 closed while the remaining cam contacts are open.

This indicates that, as seen in FIG. 3, the cam shaft of the controller is in position 1. All the relays are illustrated as deenergized so that, as presented, it may be assumed that the controller is in position 1 without current applied to the controller or that the current supply had just been turned on and no actuations have been received since current had been applied to the controller.

Let it now be assumed that the controller is placed at an intersection, for example the intersection illustrated in FIG. 1, and that power, both AG. and DC. as previously described, has been recently applied to the input terminals, that no actuations have been received and that the cam shaft is in position 1 as illustrated. In the assumed condition the relays will all be deenergized as illustrated.

The signal AG (representing signals AG and AG of FIG. 1), the green signal for phase A will be illuminated according right-of-way to traffic on Street A while signals BR and CR (representing similarly labeled signals in FIG. 1), the red signals for phases B and C respectively, will be illuminated and hold traffic on Streets B and C stopped.

With the controller in position 1, DC. power will be applied tot he timing capacitor KB from the DC. supply, represented by a plus in a square through leads 21 and 22,, resistor R1, leads 23 and 24, earn contact C24, leads 25 and 26 to capacitor KB to rapidly charge the timing capacitor. The timing capacitor KB will become fully charged but although the breakdown potential of the flasher tube FB will have been reached the tube FB will not pass current because the circuit to ground is open at cam contact C29, contact 27 of relay BD and contact 30 of relay CD.

This position, position 1, is the rest position of the controller. When at rest in position 1 the controller is awaiting demands of trafiic.

Let it now be assumed that both vehicle detectors VB, in Street B, and VC, in Street C, are actuated by vehicle traflic approaching the intersection along the respective street. It should be noted here that the condition now assumed places the controller in position 1 without knowledge of the phase last shown before the present phase A.

As a vehicle crosses over vehicle detector VB in Street B, the contacts of the vehicle detector are closed and an energizing circuit is completed to energize relay BD from the 12 volt A.C., represented by a plus in a circle, in a square, through leads 311 and 32, the coil of relay BD, leads 33, 34 and 35, contacts VB to ground 36. The relay BD closes its contacts 37, 40/41, 43, 2.7 and 44 and opens its contacts 42/41 and 45. The relay BD locks in through its contact 37 Via a circuit that may be traced from the 12 volt AC. input through leads 31 and 32, the coil of relay BD, leads 33 and 34, contact 37, leads 46 and 47, cam contact C18 to ground 36.

As a vehicle crosses over the vehicle detector VC in Street C a circuit is complete to energize the relay CD from the 12 volt A.C. through leads 31 and 50, the coil of relay CD, leads 51, 52 and 53, the contacts VC to ground 36. The relay CD thus energized closes its contacts 54, 55, 56/57, 30 and 61 and opens its contacts 57/ 60 and 62. The relay CD locks in through its own contact 54 via a circuit that may be traced from the 12 volt AC. input through leads 31 and 50, the coil of relay CD, leads 51 and 63, contact 54, cam contact C40 to ground 36.

With closure of contact 27 or contact 30 a circuit is completed to permit tube FB to pass current, if the timing capacitor KB is sufiiciently charged to the breakdown potential of the tube FB, from the charged side of the capacitor KB through lead 26, tube PB, lead 65, the coil of relay BS, leads 66 and 67, contact 30 or 27, lead 70, switch S1, to ground 36.

The last described circuit is the energizing circuit for the relay BS and relay BS thus energized closes its contacts 72 and 73. Closure of contact 73 completes an energizing circuit for solenoid SOL from the 120 Volt AC. supply through leads 2t and 74, the coil of solenoid SOL, through point 75, contact 73, lead 76 to ground 36. The energized solenoid SOL closes its contacts 77, 80 and 81 and notches a pawl into a ratchet gear (not shown), the gear is attached to the cam shaft to be rotated. Closure of contact 86 completes a circuit to discharge the capacitor KB from the charging side of the capacitor KB through lead 82, contact 80, resistor R2, lead 83 to ground 36, back to the ground side of capacitor KB. The capacitor KB thus becomes discharged and the tube FB no longer passes current. This interruption of passage of current through the tube FB causes relay BS to become deenergized and its contacts 72 and 73 open. When contact 73 opens, the energizing circuit for solenoid SOL is opened and the solenoid becomes deenergized. Upon deenergization the solenoid SOL partially rotates the ratchet gear which partially rotates the cam shaft and the cam shaft advances to position 2 to open and/ or close the several cam contacts as illustrated in FIG. 3, the cam chart.

It will be noted that both relays LB and LC are de- B energized. This is due to the fact that it has been assumed that the AC. power supply has just been applied to the controller, after absence of power for any reason, and that calls had been received on both phases B and C since power was restored.

Ordinarily, after the controller has completed at least one cycle, one of these relays, either LB or LC, will be energized while the other will be deenergized. If the phase B were the last actuated phase to be accorded right-of-way the relay LB would be energized and relay LC would be deenergized and, if the last actuated phase to be accorded right-of-way were phase C the relay LC would be energized while relay LB would be deenergized.

The phase to be next accorded right-of-way is determined by relays PB and PC, which are interlocked so that only one relay can be energized at the same time. Operation of relays PB and PC respectively predetermines the appearance of phase B or phase C respectively in positions of the cam shaft common to both phases.

Which of the relays PB or PC is energized ordinarily depends upon the trafiic actuated relay BD or CD respectively and in the event that both BD and CD are energized, then ordinarily energization of relay PB or PC depends upon energization of relay LC or LB respectively.

When both relays LB and LC are deenergized and both relays BD and CD are energized as in the assumed conditions, the controller automatically predetermines accord of right-of-way to phase C by energization of relay PC.

The controller could be designed to predetermine the phase B by operation of relay PB instead of relay PC under the assumed conditions by some variation of circuitry, if desired.

Operation of the controller through a cycle of the cam shaft will now be described briefly in general terms before describing it in detail under the assumed conditions. Position 2 of the cam shaft will cause to be displayed a yellow or clearance signal to Street A or phase A and red signals to both Street B or phase B and Street C or phase C. Position 3 of the cam shaft will cause to be displayed a green signal on one of the actuated phases either B or C, as predetermined by operation of relay PB or relay PC respectively, while the actuated phase not receiving right-of-way through a green signal display will have a red signal displayed to its trafiic with a red signal displayed to phase A traffic. Position 4 of the cam shaft will cause the right-of-way to be wntinued to the trafiic of either phase B or phase C so receiving the right-of-way while the two phases which were receiving a red signal continue to receive the same signal. Position 5 causes a yellow signal to be displayed to trafiic that in positions 3 and 4 had been receiving right-of-way via a green signal while the other phases still receive red signals. In position 6 of the cam shaft the right-of-way is recalled from the actuated phase so receiving the rightof-way to phase A, the non-actuated phase so that a green signal is displayed to phase A and red signals are displayed to phases B and C.

The next succeeding cam shaft position is position 1, the rest position. In position 1 the green signal AG displayed to phase A is illuminated via a circuit that may be traced from the AC. power supply through leads 20, 9t) and 91, cam contact C27, signal AG to ground 36. The red signal BR displayed to phase B is illuminated via a circuit that may be traced from the AC. power supply through lead 20, contact 84 of relay BL, lead 92, signal BR, lead 93 to ground 36 while the illuminated circuit for signal CR, the red signal displayed to phase C may be traced from the AC. power supply through leads 2t) and 90, contact 87 of relay CL, signal CR, leads 94 and 93 to ground 36.

The advance from position 1 to position 2 having been described above, it shall now be assumed that the controller is in its position 2.

In position 2 the cam contacts that are closed are C10, C11, C18, C20, C26, C29, C31, C33, C40 and C42.

With closure of cam contact C33 a circuit is completed to energize the relay PC. This energizing circuit may be traced from the A.C. supply through leads 20 and 95, the coil of relay PC, contact 96 of relay PB, lead 97, contact 55, contact 101/ 102 of relay LB, lead 104, contact 40/41, lead 105, contact 56/57, lead 106, contact 111/112 of relay LC, lead 14, cam contact C33 to ground 36.

The energized relay PC will close its contacts 115, 117, 122, 123 and 152 and will open its contacts 116 and 121.

With closure of cam contact C a circuit is completed to charge the capacitor KB from the D.C. power supply through part of the potential divider PDX to a point on the potential divider PD+, adjustable timing resistor R3, lead 124, cam contact C10, leads 25 and 26 to timing capacitor KB.

With the opening of cam contact C27 the illumination circuit for signal AG is opened thus extinguishing the signal AG. However, cam contact C26 is closed to complete the illuminating circuit for signal AY from the A.C. input supply through leads 20, 90 and 91, cam contact C26, signal AY to ground 36.

The interval now timed is the clearance interval of phase A and the signals at the intersection will show red signals BR and CR illuminated for phase B and phase C respectively and a yellow signal AY illuminated for phase A.

When the timing capacitor KB becomes sufficiently charged so that the charge reaches the breakdown potential of the flasher tube FB, the tube FB will pass current from the timing capacitor KB through lead 26, tube FB, lead 65, the coil of relay BS, lead 66, cam contact C29 to ground 36.

A circuit to charge timing capacitor KA is also completed, via closure of cam contact C42, from the D.C. power supply through leads 21 and 125, resistor R4, lead 126, cam contact C42, lead 127, lead 130 to capacitor KA. The charging of timing capacitor KB and the charging of timing capacitor KA begin simultaneously, however, the impedance of resistor R4 is greater than the combined impedance of the working part of adjustable timing resistor R3 and the working part of the potential divider PDX so that the capacitor KB will be charged to the breakdown potential of the tube FB before the timing capacitor KA is charged to the breakdown potential of the tube FA. The individual charging of the two timing capacitors KA and KB over separate charging circuits in position 2 is employed as a safety measure so that if the tube PE in the timing circuit, including capacitor KB should fail to pass current through the previously described circuit then the tube FA in the timing circuit, including capacitor KA would pass current through a circuit from the charging side of the capacitor KA through lead 156, tube FA, relay AS to ground 36 thereby energizing relay AS causing its contact 131 to close, which closure completes an energizing circuit for the solenoid SOL from the AC. supply through leads 20 and 74, the coil of SOL, point 75, lead 132, contact 131 to ground 36.

The energized solenoid SOL, via closure of contact 131 or 73, closes its contacts 80 and 8 1 and discharges capacitor KB as previously described through contact 80 while capacitor KA is discharged through a circuit that may be traced from the charged side of the capacitor KA through leads 130, 127, 133, contact 81, resistor R5, leads 134 and 83 to ground 36 back to the ground side of capacitor KA.

With both the timing capacitors KA and KB thus discharged the passage of current through the tube PA or PE stops thereby deenergizing relay AS or BS causing contact 131 or 73 to open, all according to which timing circuit ended the interval. Opening of contact 131 or 73, as the case may be, causes deenergization of solenoid O SOL which rotates the cam shaft, as previously described, to position 3.

With the earn shaft in position 3 the cam contacts now closed are C14, C16, C17, C13, C20, C29, C36, C38, C39, C40 and C42. It should be understood that under normal operation the timing circuit including capacitor KB, tube PB and relay BS would operate to complete the interval timed in position 2.

With the opening of cam contact C26 and closure of cam contact C39 the yellow signal AY is extinguished and the red signal AR is illuminated via a circuit that may be traced from the AC. supply through leads 20, and 91, cam contact C39, signal AR to ground 36.

The closure of cam contacts C16 and C38 prepares illuminating circuits for the signals CG, the green signal of phase C and BG, the green signal of phase B. Energization or deenergization of relays BL and CL control which signal, BG or CG, will now be illuminated.

When the cam contact C33 opens the relay PC would have deenergized except that the relay is energized through its own lock-in circuit that may be traced from the AC. input through lead 20, lead 95, the coil of relay PC, contact 96, lead 151, contact 152, lead 153, cam contact C20 to ground 36.

As previously explained the relay PC was energized in position 2 and its contact 117 was closed. Closure of contact 117 prepared an energizing circuit for the relay CL which circuit was held open by open cam contact C17.

In the present position cam contact C17 is closed so that the relay CL is now energized via a circuit that may be traced from the AC. input through leads 20, 135, the coil of relay CL, contact 117, lead 136, cam contact C17 to ground 36.

Energization of relay CL closes contact 86 and opens F contact 87. Closure of contact 86 completes the illuminating circuit for signal CG that may be traced from the AC. input through lead 20, contact 84, lead 92, contact 86, lead 137, cam contact C16, signal CG to ground 36. The signal CR is extinguished by the opening of contact 87.

The phase B red signal BR remains illuminated through the normally closed contact 84 of relay BL as previously traced.

The interval now timed is the initial interval of the phase C, the phase being determined by energization of relay PC, previously described.

The timing capacitor KB is charged from the D.C. input through part of the potential divider to a point PD+, through adjustable resistor R9, lead 140, contact 122, lead 14 1, cam contact C14, lead 25, lead 26 to timing capacitor KB. The timing capacitor KA is also charged through a circuit previously described via resistor R4 to again become a safety timing circuit. When the timing capacitor KB is sufficiently charged to reach the breakdown potential of the tube FB the tube FB will pass current thereby energizing relay BS to advance the cam shaft in a manner previously described.

In position 4 cam contacts C12, C13, C16, C17, C19. C20, C29, C34, C35, C38, C39, C41 and C42 are closed. The signal lights remain as in position 3 while the extendible vehicle interval is timed via the charging of timing capacitor KA from the D.C. supply.

In order that the charging circuit for the extendible vehicle interval be completed relay LB or LC must be energized. In position 4 with cam contact C19 closed a circuit is complete to energize the relay LC. Such energizing circuit may be traced from the AC. input through lead 20, lead 142, the coil of relay LC, lead 143, contact 115, lead 144, cam contact C19 to ground 36.

Energized relay LC closes its contacts 145, 112/113, 146, 147, 150, 160/ 161 and 163 and opens its contacts 111/112 and 161/62. With closure of contact and cam contact C34 the timing capacitor KA is charged from the D.C. input through part of the potential divider PDX to a point PD+, through adjustable timing resistor R6, contact 150, lead 154 to point 155, cam con-tact C34, lead 156, lead 130 to capacitor KA.

With the opening of cam contact C40 and contact 161/162 relay CD becomes deenergized. Relay BD remains energized even though cam contact C18 opens via a shunting circuit that may be traced from the 112 Volt AC. supply through leads 31 and 32, the coil of relay BD, leads 33 and 34, contact 37, lead 46, contact 173/ 174 of relay LB, leads 175, 176 to ground 36.

With the closure of cam contact C12 a charging circuit for the timing capacitor KB is completed from the DC. input through the potential divider PDX to a point PD+, through adjustable timing resistor R7, contact 123, lead 164, cam contact C12, leads 25 and 26 to capacitor KB.

In position 4 both minimum and maximum timing is employed, the minimum timing being extendible upon actuation of the vehicle detector associated with the phase then receiving the right-of-way during such interval.

If, for example a vehicle should cross over the vehicle detector VC the relay CD would be energized through a circuit previously described and relay CD would close its contact 61. Closure of contact 61 would complete a circuit from the left side of the capacitor KA (the changing side), through leads 136 and 156, cam contact C34, point 155, line 165, cam contact C13, resistor R3, contact 61, lead 166, contact 146, leads 134 and 33 to ground 36 to the right side (ground side) of capacitor KA to discharge the capacitor KA so as to extend the time of the interval. Multiple timely actuations of the vehicle detector VC during such interval would extend the interval to the maximum limit, so that the interval will terminate via passage of current through the tube PB when the timing capacitor KB reaches the breakdown potential of the tube PB.

Due to an absence of additional actuations of the vehicle detector VC or if additional actuations are sufiiciently far apart, the capacitor KA will become sufficiently charged to the breakdown potential of the tube FA so that the tube FA will pass current and energize the relay AS thereby closing its contact 131 which contact completes a circuit to energize solenoid SOL thereby termihating the interval via action of the extendible vehicle interval timer.

Let it be assumed that the phase C vehicle interval is terminated via the extendible vehicle interval timer. The relay AS would close its contact 131 and cause energization of solenoid SOL as previously described which would then advance the cam shaft in a manner previously explained, to the next position.

In position 5 cam contacts C15, C17, C13, C19, C20, C21, C22, C29, C31, C39, C40, C41 and C42 are closed.

In position 5, the clearance interval of the phase having been accorded right-of-way, closure of cam contact C21 completes the illuminating circuit for signal CY, the yellow signal of phase C. The circuit may be traced from the AC. input through lead 20, contact 84, lead 92, contact 86, lead 137, cam contact C21, signal CY to ground 36, while the opening of cam contact C16 extinguishes the signal CG.

Closure of cam contact C31 completes a lock-in circuit for the relay LC that may be traced from the AC. input through leads 20, 142, the coil of relay LC, contact 145, lead 167, cam contact C31 to ground 36. A timing circuit is completed from the DC. supply through part of the potential divider PDX to a point PD+ through adjustable timing resistor R16, contact 62, lead 1713, contact 147, cam contact C15, leads 25 and 26 to timing capacitor KB thereby charging the capacitor KB. It should be noted in the above described charging circuit, between adjustable timing resistor R and lead 176 is a resistor R11 shunted by contact 62. The contact 62 is controlled by the relay CD which relay is energized via closure of the vehicle detector contact VC.

If during the clearance interval for phase C, now being timed, a call should be received from the vehicle detector VC, the relay CD would become energized, as previously described, and open its contact 62. Or, if, as will be e"- plained below, the previous interval, position 4 of phase C, should terminate via the maximum limit timer, the relay CD will be energized and open its contact 62. The opening of contact 62 will open the shunting circuit of resistor R11 and the resistor R11 will become an effective part of the charging circuit by which the capacitor KB is charged during this interval, position 5, thereby increasing the impedance in the charging circuit and effectively increasing the time the yellow signal CY is displayed.

If, either by action of the maximum limit timer or by a call during the clearance interval of the phase C the relay CD becomes energized, relay CD will lock-in and remain energized until the inception of the extendible vehicle interval of the next cycle during which the phase C is displayed and then relay CD will become deenergized. If, for any reason the relay CD should be energized in position 5, the relay will remain energized for memory purposes as explained below.

At termination of the interval timed in position 5 the cam shaft is advanced to position 6, the phase A minimum green interval. In position 6 cam contacts C18, C25, C27, C29, C31 and C 10 are closed. The timing capacitor KB is charged from the DC. supply through part of the potential divider PDX to a point PD+, through adjustable timing resistor R12, lead 171, cam contact C25, leads 25 and 26 to capacitor KB.

Closure of cam contact C27 completes a circuit to illuminate the signal AG, the green phase A signal, the circuit being previously described. The opening of cam contact C17 opens an energizing circuit for the relay CL while the opening of cam contact C26 causes the relay PC to become deenergized. Deenergized relay CL opens contact 86 and closes contact 87. The opening of contact 86, as well as the opening of cam contact C21, cause the signal CY to be extinguished while closure of contact 37 causes signal CR to become illuminated through a circuit previously described.

The relay LC remains locked in as previously explained to indicate the last actuated phase, before the present phase A, was phase C.

When the charge on the timing capacitor KB reaches the breakdown potential of the tube FB the tube FB will pass current to cause the advance of the cam shaft to position 1, which position is the rest position of the controller.

It was previously assumed that both phase C and phase B actuations, via their respective vehicle detectors VC and VB, had been obtained. It should be noted that during the entire cycle above described the relay BD remains energized through a circuit previously described, including cam contact C18 or while the controller was in position 4, by a shunting circuit traced from the coil of relay BD through leads 33, 34, contact 37, lead 46, contact 173/174 of relay LB, lead 175, lead 176 to ground 36.

-If there were no calls, as would be indicated by the relays CD and BD both being deene-rgized at this time, the controller would rest in position 1, however, since, as has been assumed a phase B call is present, as indicated by the relay BD being energized, the controller advances to the next position, position 2 as the timing capacitor KB is rapidly charged from the DC. supply via a circuit previously described including resistor R1 and the tube FB passes current from the charging side of the capacitor KB through lead 26, tube FB, lead 65, the coil of relay BS, leads 66 and 67, contact 27, lead 70, switch S1 to ground 36.

In position 2 the relay PB is energized through completion of a circuit from the AC. supply through leads 20 and 177, the coil of relay PB, contact 116 to point 180, contact 43, to point 181, contact 112/113, lead 114, cam contact C33 to ground 36.

The relay PB closes its contacts 182, 183, 186, 187 and 190 and opens its contacts 185 and 96. Closure of contact 182 completes a lock-in circuit for the relay PB that may be traced from the A.C. input through leads 20 and 177, the coil of relay PB, contact 116, point 180, contact 182, lead 153, cam contact C20 to ground 36. The contact 1 83 prepares an energizing circuit for the relay BL. As previously described in position 2 above, the green signal AG becomes extinguished and the yellow signal AY is illuminated while the red signals BR and CR remain illuminated.

The advance into position 3 is as described above. In position 3 the relay LC becomes deenergized with the opening of cam contact C31 while the relay BL is energized via a circuit that may be traced from the AC. input through leads 20 and 191, the coil of relay BL, contact 183, leads 136, cam contact C17 to ground 36. With relay BL energized its contact 84 is opened and its contact 85 is closed.

The signal AY is extinguished and the signal AR is illuminated as previously described. The opening of contact 84 extinguishes the signal BR and closure of contact 85 completes an illuminating circuit for signal BG from the A.'C. input through leads 20 and 90, contact 87, contact 85, lead 192, cam contact C38, signal BG to ground 36. The signal OR is illuminated through a circuit previously described.

Position 3, now the phase B initial interval, is timed by charging the capacitor KB from the DC. input through part of the potential divider PBX to a point PD+, through adjustable timing resistor R13, lead 193, contact 186, lead 141, cam contact C14, leads 25 and 26 to capacitor KB. The advance into the next position would be as previously described.

In position 4 the relay LB would become energized via a circuit that may be traced from the AC. supply through leads 20 and 194, the coil of relay LB, lead 195, contact 190, lead 144, cam contact C19 to ground 36. The relay LB when energized closes its contacts 202, 172/173, 196, 102/103, 197, 200, and 201 and opens its contacts 101/102 and 173/174.

Closure of the contact 196 would complete a lock-in circuit for the relay through a circuit that may be traced from the AC. supply through leads 20 and 194, the coil of relay LB, contact 196, lead 167, cam contact C31 to ground 36.

The vehicle interval of phase B is timed by the extendible vehicle timer by charging the timing capacitor KA from the DC. input through part of the potential divider PDX, to a point PD+ through the adjustable timing resistor R14, contact 201, lead 154, point 155, cam contact C34, lead 156, lead 130 to capacitor KA while the maximum limit control is timed by charging the capacitor KB from the DC. input through part of the potential divider PDX to a point PD+, through the adjustable timing resistor R15, contact 187, lead 164, cam contact C12, leads 25 and 26 to capacitor KB.

As previously explained, relative to position 4 above, the interval may be terminated either by the extendible vehicle timer or, by the maximum limit timer if the extendible timer is extended, via trafiic actuation of the phase B vehicle detector during such interval, to the maximum limit.

The extendible vehicle timer is extendible to the maximum limit by timely actuations of the vehicle detector VB via phase B traffic during the charging of the capacitor KA. The relay BD had become deenergized at the beginning of position 4 by the opening of cam contact C18. If during the extendible vehicle interval a vehicle should cross over the vehicle detector and close the contacts VB the relay -DB Would become energized through a circuit previously described. Energized relay BD would close its contact 44 to complete a circuit to ground from the charging side of the capacitor KA through leads 130 and 156, cam contact C34 to point 155, lead 12 165, cam contact C13, resistor R8, contact 44, lead 203, contact 197, lead 134, lead 83 to ground 36.

Assuming that due either to an absence of vehicle actuations of the phase B vehicle detector VB or additional actuations sutficiently far apart to permit the charging of capacitor M to the breakdown potential of the tube FA, the tube FA will then pass current to energize the relay AS thereby closing contact 131 to complete an energizing circuit for the solenoid SOL to cause the advance of the cam shaft to the next position, position 5.

In position 5 the green signal BG is extinguished and the yellow signal BY is illuminated via a circuit from the AC. input through leads 20 and 90, contact 87, contact 85, lead 192, cam contact C22, signal BY to ground 36.

The interval is timed by the charging of the capacitor KB to the breakdown potential of the tube FB from the DC. supply through part of the potential divider PDX to a point PD+, through adjustable timing resistor R17, contact 45, lead 208, contact 200, cam contact C15, leads 25 and 26 to capacitor KB.

As previously described for phase C in position 5 the interval now timed may be extended via trafiic actuation of the phase B vehicle detector during such interval or by termination of the extendible vehicle interval via the maximum limit timer. Actuation of the vehicle detector VB during such interval, or termination of the previous interval via the maximum limit causes energization of the relay BD which relay then opens its contact 45, which contact when closed, shunts resistor R16 in the charging circuit previously described between resistor R17 and line 208. The opening of contact 45 effectively increases the impedance in the charging circuit so as to increase the amount of time necessary to charge the capacitor KB to the breakdown potential of tube PB.

The controller advances into position 6, as previously described, and causes deenergization of relay BL via open cam contact C17, and relay PB via open cam contact C20.

With deenergization of relay BL the contact 84 is closed to cause signal BR to become illuminated and contact 85 becomes open to break the circuit to the cam contacts C38 and C22 leading to signal lights BG and BY respectively.

Position 6 is similar to position 6 described above except that the relay LB is energized, indicating the last actuated phase shown before phase A, was phase B.

It was above assumed that the interval timed in position 4, in each description was terminated via action of the capacitor KA, the capacitor timing the extendible vehicle interval, becoming charged to the breakdown potential of the tube FA and thereby terminating the intcrval via the extendible vehicle interval timer.

Returning momentarily to the first description above, to position 4 of phase C, let it be assumed that due to multiple timely actuations of vehicle detector VC the capacitor KA is repeatedly discharged and the charge is kept from reaching the flash voltage of tube FA so as to extend the extendible vehicle interval to the maximum limit. Thus the capacitor KB will become charged to the breakdown potential of the tube PB and, as previously described the tube FB will pass current and energize the relay BS. The relay BS will close its contact 72 to complete a circuit from the 12 volt A.C. supply through leads 31 and 50, the coil of relay CD, leads 51 and 52, contact 163 of relay LC, lead 204, contact 72, cam contact C35 to ground 36.

Since in position 4 cam contact C40 is open, the relay CD locks in through a circuit that may be traced from the 12 volt AC. input through leads 31 and 50, the coil of relay CD, leads 51 and 63 to contact 54, lead 206, contact /161, lead 207, contact 77, lead 176 to ground 36. The cam contact C40 will close before contact 77 of SOL opens so energized relay CD will remain energized via completion of a circuit previously traced including lock-in contact 54 and cam contact C40.

The energized relay CD will remain energized and reassess? 13 member and recall the controller to the phase C as soon as possible. If there is no phase B call to cause the controller to accord right-ot-way to phase B, the controller will return to phase C after right-of-way has been accorded to phase A.

If a call for phase B were then present, or a subsequent phase B call were received before the termination of the phase A green period, then the phase B would receive right-of-way following the phase A and the phase C would follow the phase A which would be displayed after the phase B.

If a cycle including phase B should occur while the relay CD is held energized for memory purposes the position 4 during the phase B would find the cam contact C40 open. In order that the relay CD remains energized, a circuit is completed to shunt such holding circuit from the coil of relay CD through leads 51 and 63, contact 54, lead 206, contact 161/ 162, lead 17-6, to ground 36.

Returning now momentarily to the phase B, position 4, let it be assumed that phase B, position 4, will terminate via the maximum limit as described above relative to phase C, position 4. During phase B the relay LB will be energized so that closure of contact 72 by energization of relay BS of the maximum limit circuit will cause relay BD to become energized via a circuit that may be traced from the 12 Volt AC. input through leads 31 and 32, the coil of relay BD, leads 33 and 205, contact 202, lead 204, contact 72, cam contact C35 to ground 36.

With the controller in position 4 the cam contact C18 is open so that the lock-in circuit for the relay ED is completed from the AC. input through leads 31 and 32, the coil of relay BD, leads 33 and 34, contact 37, lead 46, contact 172/173, lead 207, contact 77, lead 176 to ground 36. Before the contact 77 opens the cam contact C18 will close and the relay BD will then lock-in through its contact 37 and through cam contact C18 (as previously traced), to remember and return the controller to accord right of way to phase B as soon as possible as described with reference to a phase C memory returning the controller to phase C.

If a phase C should be displayed in the next cycle the cam contact C18 will be open in position 4 and a shunting lock-in circuit will 'be completed from the coil of the relay BD through leads 33 and 34, contact 37, lead 46, contact 173/174, lead 175, lead 176 to ground 36 so that the relay BD will not become deenergized during that cycle.

And now with the controller in phase A position, its rest position, having last served phase B, let it be assumed that a call for phase C is received via trafiic actuation of the detector VC.

As previously described, energization of relay CD, closure of contact 30, completion of the energizing circuit for relay BS, closure of contact 132 and subsequent energization of SOL follow to cause the advance into position 2.

In position 2 the relay PC is energized from the AC. supply through leads 20 and 95, the coil of relay PC, contact 96, lead 97, contact 55, contact 102/103, cam contact C11 to ground 36. The relay CL is energized by closure of contact 117 and cam contact C17 and the phase C green signals are illuminated when the controller advances into its position 3, all as previously described. Positions 3, 4 and are substantially the same as previously described for phase C, position- s 3, 4 and 5 except that the relay LB, which was energized in the last position 1, indicating the last actuated phase served was phase B, is deenergized in position 3 by the opening of cam contact C31. In position 4 relay LC is energized through contact 115 and cam contact C19 as previously described in detail until the cam contact C31 opens in the next cycle of operation.

If the controller should be caused to be cycled by a phase C vehicle actuation after having last served phase C, the controller will advance through its cycle'as previously explained except that the energizing circuit for relay PC in position 2 shall include contact 96, lead 97, contact 55, contact 101/102, lead 104, contact 41/42, lead 210, and cam contact C11. In position 3 the relay LC would become deenergized but in position 4 would become energized again through circuits previously described. The relay LC would then remain energized until the next position 3 of the controller.

Let it now be assumed that the controller is at rest in position 1, having last served phase B and a phase B call is received. Via action of the relays BD, BS and SOL in sequence, the controller will advance into position 2. In position 2 the relay PB is energized via a circuit including contact 116, point 180, contact 43, point 181, contact 57/60, lead 106, contact 111/112 and cam contact C33.

The relay LB energized in positions 6, 1 and 2, indicating the last phase served was phase B, is deenergized in position 3 and energized again in position 4. The phase B right-of-way is accorded in positions 3, 4 and 5, as previously described, and the controller advances into phase A, position 6 with relay LB remaining energized and, in absence of subsequent calls, rests in position 1.

Let it now be assumed that the controller is in the phase A green position 6 or position 1, having last served phase B and that there are no present calls on the controller. Further assume a call is now received for phase B, via vehicle actuation of the detector VB. The relay BD will become energized and affect its contacts as previously described. A circuit, including contacts 116, 43, 57/60 and 111/112 is prepared so that the relay PB may become energized when cam contact C33 closes in position 2. Let it further be assumed that, during the phase A green period, positions 6 and 1, after the phase B call is received, a call for phase C is received via actuation of the detector VC. The relay CD will now become energized and affect its contacts as previously described. With relay CD energized, the prepared circuit for relay PB is opened at now open contact 57/60 of relay CD and a circuit including contacts 96, 55 and 102/103 is prepared to cause energization of relay PC upon closure of cam contact C11 in position 2. When relay PC becomes energized a lock-in circuit previously described, including contacts 96 and 152 and cam contacts C20 is completed during positions 2, 3, 4 and 5.

The controller advances through its cycle and displays the phase C signals, similar to that which has been described, while the relay ED is held in an energized condition.

Upon the return to phase A, position 6, after having displayed phase C, a circuit is prepared for energization of relay PB which circuit includes contacts 116, 43' and 112/113 so that in position 2 when the cam contact C33 closes the relay PB will become energized. The still energized relay BD will cause closure of contacts to advance the controller into position 2 and when relay PB is then energized the controller will continue through its cycle and display the phase B, all as previously described.

The last described action of the controller illustrates that the controller will give preference to the actuated phase not last accorded right-of-way as between the two actuated phases, even though a call for the actuated phase last accorded rightof-way precedes a call from the actuated phase not last displayed, up to the phase A clearance period. This is further illustrated when consideration is given to the situation where the controller is in phase A, position 6 or 1, without any calls, having last accorded right-of way to phase C and a call for phase C is received.

The call for phase C will cause energization of relay CD which relay will efiect its contacts as previously described and prepares a circuit for energization of relay PC, through a circuit including contacts 96, 55, 101/102 and 41/42. This circuit may be completed in position 2 by closure of cam contact C11.

Let it now be assumed that a phase B call is received after the phase C call is received and before the advance of the controller into position 2. The phase B call results in energization of relay BD which relay will efiect its contacts as previously described and cause the opening of contact 41/42 thereby breaking the prepared circuit for relay PC, and close contact 43 which prepares an energizing circuit for the relay PB. The prepared circuit for relay PB including contacts 116, 43, and 112/113 is completed in position 2 by closure of cam contact C33. After the initial energization of relay PB in position 2 the relay PB locks in through a previously described circuit including contacts 116, 182 and cam contact C20. The relay PB is held energized in positions 2, 3, 4, and 5, while the controller displays the phase A yellow signal, position 2, and the phase B green signal in positions 3 and 4 and the phase B yellow signal in position 5. During the cycle the relay CD is held energized, as previously described so that when the controller advances into position 6 the relay PC will have an energizing circuit prepared including contacts 36, 55 and 102/ 103. The controller will proceed in its cycle and advance into position 2 where the relay PC will be energized as cam contact C11 closes. Energization of relay PC completes a lock-in circuit previously desscribed, through contacts 96, 152 and cam contact C20, which lock-in circuit is held completed in positions 2, 3, 4 and 5 of the ensuing cycle. The phase C will be displayed in positions 3, 4 and 5 and the controller will advance, as previously explained to positions 6 and then to position 1, the rest position, and await further demands of trafiic.

The switch S1 will now be explained. The switch S1 may be used as a coordination control switch when the switch is associated with and controlled by an external master timer or master cyclic controller means.

Master control over controllers in a coordinated system is fully discussed in U.S. Patent 2,152,138, issued to Harry A. Wilcox and John L. Barker as co-inventors on April 25, 1939.

The switch S1, which pivots on its upper terminal, may be opened by moving the moving part of the switch to the right to point P1.

For coordinated control the switch S1 would be closed only for a short duration during each cycle. If during such closure the controller was in, or moved into its position 1 and there was a phase B or a phase C call, or both, then the controller would be permitted to advance into its position 2 and thus terminate its phase A green period.

By coordinated control of the controllers advance from position 1 to position 2, two or more controllers may be used in a control system and each controller coordinated with the other so that if two or more controllers were to terminate their phase A green period such termination would be together or at an offset as desired.

If coordinated control were not desired the switch S1 would be closed during the entire cycle of the controller and in effect, eliminating its control over the circuit in which it is located.

The use of contact 185 of relay PB and contact 121 of relay PC will now be explained. It should be noticed that cam contacts C41 and C36 are connected in parallel between lead 211 and lead 25. The cam sequence chart in FIG. 3 shows cam contact C36 closed in position 3 and cam contact C41 closed in positions 4 and 5. If, for example, the controller were in positions 3, 4 or 5 and for one reason or another, the power supply should fail, all the relays then energized would become deenergized. Upon restoration of power those relays, normally held energized through lock-in circuits, such as PB, PC, LB and LC and the relays CL and BL depending upon energization of relay PC and PB respectively, would remain deenergized. With relays PC and PB both deenergized the red signals CR and BR would be illuminated and even though the cam shaft of the controller may be in position to illuminate phase B or C green or yellow signals, due to the relay BL and CL being deenergized, the red signals of both the phases B and C would be illuminated through circuits previously traced. As previously described, the red signal AR is illuminated in positions 3, 4 and 5 through cam contact C39.

This siutation would cause red signals to be displayed to all phases of traffic at the controlled intersection at the same time.

In order that the all-red period is not held to the detriment of any potential traific flow, a rapid charging circuit is completed in positions 3, 4, and 5 from the DC. supply through leads 21, 22, resistor R1, lead 23, contact 185, contact 121, lead 21 1, cam contact C36 (in position 3) or cam contact C41 (in positions 4 and 5), leads 25 and 26, to capacitor KB. The cam shaft is rapidly advanced from positions 3, 4 or 5 to position 6. In position 6 the rapid charging circuit is opened as both cam contacts C36 and C41 are then open.

The controller arrives in position 6, the minimum interval of phase A, and times the interval as previously described. The controller then advances into position 1, the rest position.

If there had been no calls for phase B or phase C between the restoration of power and the arrival of the controller into position 1, the controller would then come to rest in position 1 and await the further demands of trafiic.

Summarizing the cooperation among the several relays controlling which side street is to be served, the relays LB and LC remember the side street phase last accorded righ-of-way, the relays BD and CD remember trafiie actuations from phase B and phase C respectively, and relays PB and PC predetermine which of these phases will be accorded right-of-way in the part of the cycle allocated potentially to either side street phase, in accordance with the conditions of relays LB and LC and BD and CD. Thus relays PB and PC select the timing circuits for B or C respectively to be employed and their associated relays BL and CL select the B or C signals respectively to be displayed for corresponding accord of right-of-way in the positions of the cam shaft common to both side street phases.

The above is the normal operation when either relay LB or relay LC remains locked in at the end of the phase A green period to remember which side street phase was last served. It will be noted that provision has also been made to predetermine one of the side street phases in event of loss of history or memory of the phase last served, as by the release of the locked-in relay LB or LC, as the case may be, in the event of interruption and return of power. It will be noted that relays BD and CD would also release in event of loss of power, and thus further accord of right-of-way to phase B or phase C would then depend on further traffic actuation after power is restored.

It will be understood by those skilled in the art that various other modifications in the structural details, or in the arrangements of the parts, or changes in the design herein exemplified may be made without departing from the spirit of the invention within the scope of the claims.

I claim:

1. Trafiic signal control apparatus for two minor roads intersecting a major road, including means individual to each of the minor roads for actuation by trafiic in the respective minor roads, a cyclic controller including cyclic switching means having a sequence of positions for providing a cycle of operation for such trafiic signal control including one position in a first part of such cycle for accord of right-of-way to said major road and another position in a second part for potential accord of rightof-way commonly to either of said minor roads and then returning to said first part for accord of right-of-way to said major road, means'for remembering in said first part of said cycle which minor road was last accorded right-of-way in the preceding cycle, means for predetermining accord of right-of-way in the same said other position in said second part of said cycle to one of said minor roads in response to actuation of said trafiic actuated means for said one minor road alone irrespective of which minor road is remembered by said remembering means as the last to be accorded right-of-way and means including connections with said controller and said remembering means and said traffic actuated means for predetermining accord of right-of-way in said second part of said cycle to one of said minor roads in response to actuation of said traffic actuated means for both said minor roads when said remembering means remembers the other of said minor roads to be the last to be accorded right-of-way.

2. Traflic signal control apparatus as in claim 1 and in which such operation of said remembering means depends on continuity of a power supply for said apparatus, and including means for predetermining accord of right-ofway to one of said minor roads in response to actuation of the traflic actuated means thereof after connection of said power supply in absence of operation of said remgmbering means to so remember either of said minor roads in event of connection of such power supply after any disconnection of such power supply.

3. A traffic signal control apparatus as in claim 1 and including individually adjustable timing means for timing such accord of right-of-way to the respective roads, and means forming a part of said predetermining means for selecting between the timing means for the two minor roads to make efiective for so timing the accord of rightof-Way to the minor road during the said another position of said second part of said cycle the timing means individual to such last named minor road.

4. A trailic signal control apparatus as in claim 1 and including means for storing through and after the accord of right-of-way to either minor road and until accord of right-of-way to the other minor road any traflic actuation occurring on such other minor road just prior to and during such accord of right-of-way.

5. A tratfic signal control apparatus as in claim 1 and said predetermining means including mutually interlocked relay means operated at least in part before and during said second part of said cycle and released at the beginning of the following first part of said cycle for so determining the accord of right-of-way to the minor road' 6. Trafiic signal control apparatus for two minor roads intersecting a major road, including means individual to each of the minor roads for actuation by traffic in the respective minor roads, a cyclic controller having a cycle of operation for such traffic signal control including a first part of such cycle for accord of right-of-way to said major road and a second part for potential accord of right-of-way to either of said minor roads and then returning to said first part for accord of right-of-way to said major road, relay means controlled by said controller for remembering in said first part of said cycle which minor road was last accorded right-of-way in the preceding cycle, other relay means controlled by said remembering means and said controller and said trafiic actuated means for according right-of-way next in said second part of said cycle to the first of said minor roads in response to actuation of said traffic actuated means for said first minor road alone and also in response to actuation of said traffic actuated means for both said minor roads when said remembering means remembers the second of said minor roads as the last previously accorded right-of-way, and said other relay means controlled by said relay remembering means and said controller and said traffic actuated means for according right-of-way next in said second part of said cycle to the second of said minor roads in response to actuation of said traffic actuated means for said second road alone and also in response to actuation of said trafiic actuated means for both said minor roads when said remembering means remembers the first of said minor roads as the last previously accorded right-of-way.

7. Trafiic signal control apparatus for two minor roads intersecting a major road, including means individual to each of the minor roads for actuation by trafiic in the respective minor roads, a cyclic controller having a cycle of operation for such trafiic signal control including a first part of such cycle for accord of right-of-way to said major road and a second part for potential accord of rightof-way to either of said minor roads and then returning to said first part for accord of right-of-way to said major road, relay means having alternate modes of operationfor predetermining accord of right-of-way in said second part of said cycle to one of said minor roads in one mode and to the other minor road in the other mode, further relay means having further alternate modes of operation for remembering such accord of right-of-way to said one minor road in the first further mode and such accord of right-of-way to said other minor road in the second further mode, operating circuit means for the first mentioned relay means controlled by said cyclic controller and by said further relay means and by said traflic actuated means for operating said first relay means to said one mode in response to a combination of actuation of the traffic actuated means in said one minor road and non-actuation of the traffic actuated means in said other minor road, and also in response to a combination of actuation of the traflic actuated means in said one minor road and operation of said further relay means to said second further mode, operating circuit means for operating said first relay means to said other mode in response to a combination of actuation of said traific actuated means for said other minor road and non-actuation of the trafiic actuated means on said one minor road and in response to a combination of actuation of said traffic actuated means for said other minor road and operation of said further relay means to said further first mode.

8. A traffic signal control apparatus as in claim 7 and in which said first relay means includes a pair of relays interlocked to prevent concurrent operation of both relays but permitting operation of one relay for one mode and the other relay for the other mode, and in which said further relay means includes a further pair of relays one of which relays is operated at the end of accord of rightof-way to one minor road and until the next accord of right-of-way to either minor road for said further first mode and the other of which relays is operated at the end of accord of right-of-way to the other minor road and until the next accord of right-of-way to either road.

9. A traffic signal controller for twominor roads intersecting a major road, a cyclic switching mechanism having a cycle of positions through which it is adapted to be operated and including one position in a first part of said cycle for operation of the traffic signal to accord right-of-way to said major road and another position in a second part of said cycle for potential operation of the traflic signal for potential accord of right-of-way to either of said minor roads, relay means individual to the respective minor roads for actuation by traffic therein, means for operation of said cyclic switching mechanism from said first part to said second part of said cycle and return to said first part in response to actuation of either of said traffic actuated relay means, second relay means including a pair of interlocking relays for predetermining accord of right-of-way to one minor road in said other position of said cyclic switching mechanism by operation of one relay and accord of right-of-way to the other minor road in the same said other position of said cyclic switching mechanism by operation of the other relay of said pair, third relay means including two relays individually operable from accord of right-of-way to one minor road and the other minor road respectively to the next accord of right-of-way to either minor road, and

circuit means for controlling the respective relays of said second relay means in response to the respective trafiic actuated relay means and the third relay means for such accord of right-of-Way to Whichever of said minor roads is actuated alone and for such accord of right-of-way to the other minor road in one cycle after accord of right-of-Way to one minor road in the next preceding cycle.

10. A traffic signal controller as in claim 9, and in which said cyclic switching mechanism includes additional positions following the respective said one and other positions in its cycle for clearance of trafiic accorded right-of-Way.

References Cited in the file of this patent UNITED STATES PATENTS 2,114,968 Nein Apr. 19, 1938 2,188,348 Haugh Jan. 30, 1940 FOREIGN PATENTS 416,588 Great Britain Sept. 18, 1934

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