US3234505A - Traffic control system of the actuated type with improved time control - Google Patents

Description

Feb. 8, 1966 c. L. DU VIVIER 3,234,505

TRAFFIC CONTROL SYSTEM OF THE ACTUATED TYPE WITH IMPROVED TIME CONTROL Filed Aug. 18, 1961 3 Sheets-Sheet 1 VARIABLE BIAS -303 2o GENERATOR 7 8 51 mWTH 3 zx T augluLs CHARGING TERMIN.

L2 CIRCUIT 324d UNIT Q l .1. 305 3 V 307 J 308 A 304 MAXIMUM 302b,

UMIT NORMAL BANK Q63 TIMER INTERVAL 3 11I .L .L'.[ J. I. T l RELAY 1 m? BQNK i BANK l l g \.6HSTEPP|NG swrrcu BANKS I TO 6 +MOTOR MAGN ET 3l4 INVENTOR. CHARLES L.DuV|vn-:R

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ATTORNEY Feb. 8, 1966 c.| DU VIVIER 3,234,505 TRAFFIC CONTROL SYSTEM OF THE ACTUATED TYPE WITH IMPROVED TIME CONTROL Filed Aug. 18, 1961 5 Sheets-Sheet 2 i TO BANK"! r POSITIONS 2+6 72o FIG. 30

T0 coN'rAcTps'! T0 BANK 4 3l4u' POSITIONS 2+6 T0 r CONTACT I) 3040 3g 302b TO BANKI 1 A -3b WIPER so I -32 INVENTOR. {CONTACT 6 I CHARLES L.DUVIVIER H I BY I Ma YEW TO RECALL SWITCHES ATTORNEY 3 Sheets-Sheet 5 TO CONTACT .Q,

c. L. DU VIVIER TRAFFIC CONTROL SYSTEM OF THE ACTUATED (FLASH OR TRIGGER VOLTAGE) TYPE WITH IMPROVED TIME CONTROL Feb. 8, 1966 Filed Aug. 18, 1961 (MINIMUM ALLOWABLE GAP LEVEL) INVENTOR. CHARLES L.DUV|V|ER ATTORNEY RENAKIDEI PA A United States Patent 9 3,234,505 TRAFFIC CONTROL SYSTEM OF THE ACTUATED TYE WITH IMPROVED TIME CONTROL Charles L. Du Vivier, Darien, Conn, assignor to Laboratory for Electronics, Inc, Boston, Mass, a corporation of Delaware Filed Aug. 18, 1961, Ser. No. 133,020 9 Claims. .(Cl. 340-37) This invention relates to trafiic control systems for control of right-of-way of trafilc at a junction of trafiic lanes. More particularly the invention relates to an improved traflic signal control system, of the actuated type, employing one or more vehicle detector devices in the intersecting lanes, trafiic right-of-way signals at the intersection and a traffic signal controller of the full actuated type for providing transfer of right-of-way between the several intersecting streets or lanes successively.

for timed periods, such transfer being made in response to trafiic actuation by waiting traffic and timing, of one or more intervals of a right-of-way period, responsive to actuation of right-of-way traffic.

In the present system, actuation of a traffic detector in a trafiic lane in which the stop signal. is being displayed causes response which determines that rightf-Way shall be transferred to that lane at the first opportunity. If there is no traffic entering the intersection from the lane in which the go signal is being displayed, the right-ofway is transferred from the latter'lane to the former lane, usually with an intervening caution signal display for. a brief period for the latter lane.

If traffic is moving in the lane in which the go signal is displayed actuation of the traffic detector in the lane in which the stop signal is being displayed causes the right-of-way to be transferred thereto at the first break of a predetermined time in the moving of right-of-way traffic. If no such break occurs in the right-of-way traffic, right-of-way will be transferred at the end of a predetermined maximum period and automatically lane. I

In this system, actuation of a vehicle detector by returned after serving the waiting 'traffic on the other;

right-of-way traflic during the go period causes such go signal period to be extended under certain conditions. The go period for each traflic lane is divided into two parts. During the first part of this period any actuation of the traffic detector in the lane in which the go Signal is being displayed is of no effect. 'Thisfirst part of the go period, called the initial interval, is to allow for standing trafiic to get into motion.

After the expiration of the initial interval the go signal will continue to be displayed for an interval of time at least suflicient for a moving vehicle to progress from the trafiic detector through the intersection. This last named interval is called the extendible vehicle interval. I

During the vehicle interval, actuation by trafiic having the right-of-way extends the right-'of-way period for a time interval sufficient to allow the actuating vehicle' 'ice Afterfailure of reset of the resettable period, the rightof-way interval is terminated after a timed period sufficient to permit passage of the last eifective actuating vehicle through the intersection.

The present system includes a new and more efficient means and manner of timing and extending the time increments of the vehicle interval in response to actuation of right-of-way traffic.

My present controller employs one composite timer for timing the entire vehicle intervals, which includes the resettable part of the vehicle interval as Well as the passage time.

My improved apparatus includes an improved composite time control circuit employing linear-with-time charging of a timing capacitor and controlled bias voltage application to the timing capacitor. Electrical isolation of the timing capacitor provides for operation of a trigger circuit without effect on the capacitor.

Operation of the trigger circuit is accomplished by the presence of a predetermined total voltage across the timing capacitor and an additive bias voltage in series. The predetermined total voltage may result from the accumulated charge on the timing capacitor plus a steady bias voltage or may result from the accumulated charge plus a variably increased bias voltage, with both the charge and the bias voltage. independently controlled applied to the capacitor. The predetermined total voltage is sufiicient to overcome a high fixed cut-off grid bias at the input tube of the trigger circuit to operate the trigger circuit.

Thus, dual, independent control of the voltage of a timingcapacitor, with the capacitor electrically isolated from the trigger circuits provides for the simultaneous timing of a progressively reduced resettable vehicle time increment and a constant length passage tirne with the passage time extending beyond the resettable vehicle time increment a varying time, which depends upon the amount of time the associated resettable vehicle time increment has been reduced.

The present invention discloses an improved full actuated local traflic signal controller which may be part of a traflic control system, for use at an intersection in which the go or green period of each phase of the traffic signal cycle includes a locally adjustable, stable initial. interval and an extendible interval with the extendible portion of the green period made up of multiple parts. This initial portion, which is unextendible, is for the purpose of clearing out all vehicles which have arrived and are waiting during the last red period, between the detector and the intersection stop-line.

After termination of the initial interval the extendible portion of the green period may be timed if there is a demand for transfer of might-of-way.

If there is no demand for transfer of right-of-way the controller moves into the position in which the extendible interval may be timed, and assumes what may be referred to as a rest condition.

In the rest condition a maximum limit timing circuit,

which may time the maximum time the controller may be permitted to remain in the exte ndible interval, after demand for transfer of the right-of-way is received, is

forced to rest and a variable bias generating unit, which is used to set the passage time, and reduce the allowable gap time from a maximum allowed gap time to a minimum allowed gap time, is held in quiescent state so that the maximum allowed gap time is not reduced.

During such rest condition a linear-With-tirne charging circuit is operating and charging a timing capacitor linearly, over a steady bias voltage impressed by the quiescent variable bias generating unit.

In the event of absence of actuation by traflic receiving right-of-way and absence of actuation demanding transfer of right-of-way the charge on the timing capacitor may increase to or above a value that would normally cause termination of the interval without resulting in termination of the interval.

In the event of actuation by traffic receiving right-ofway the linear charge on the timing capacitor may be discharged to again charge from its starting or base value. This action may be repeated as often as there are actuations by traflic receiving right-of-way so long as there is no demand for transfer of right-of-way.

If the controller moves into a position in which the extendible interval is timed with a demand for transfer being made, operation of the maximum limit timer, the variable bias generating unit and the linear-with-time charging circuit are initiated simultaneously as soon as the wiper contacts of the several banks of line switches make contact with the position in which the extendible interval is timed. Operation of these three circuits establishes and starts to time a maximum time limit that the controller may remain in the current position; starts to time a preset time increment referred to as a passage time and starts to reduce, from a maximum to a minimum time, the time during which an actuation by traffic having rightof-way must occur, measured from the start of the interval or the last actuation by traflic having right-of-way, in order to extend the green period of the phase.

It the controller moves into an extendible interval position without a demand for transfer of right-of-way the controller will assume a rest condition until such time as a demand for transfer of right-of-way is received. If at the time such transfer demand is received the charge on the timing capacitor is at or above the value that would normally cause termination of the interval; upon such transfer demand, then termination of the interval will occur immediately after receipt of such demand for transfer.

If at the time of such transfer demand the charge on the capacitor is below the value at which termination of the interval may occur, due to repeated discharge of the capacitor by actuation of right-of-way traffic or due to the controller not having been in the position sufliciently long to have the value of the charge increased to such level, then the interval will not immediately terminate. The maximum limit timer will become operative and begin to time the maximurn'time limit that the controller may now remain in the current position. The variable bias generating unit will start to reduce from a maximum toward a minimum time during which an actuation from right-of-way trafiic must be received in order to extend, for another time increment, the extendible interval. This time, during which such actuation by right-of-way trafiic must be received, measured from thestart of the interval or the last actuation, which ever last occurred, is re ferred to as the allowed gap time. This allowed gap time is variable and may be reduced from a maximum gap time to a minimum gap time over a preset time period.

During timing of the extendible portion of the green period when there is a demand for transfer of right-ofway each actuation of the detector on the street having right-of-way permits the green time to be tentatively lengthend by a preset time increment, referred to as a passage time. So long as the time gap between actuations of two successive vehicles of right-of-way traflic is less than the time-reduced allowable gap, the preset time increment or passage time may bereset so that the passage time will begin to be retimed. This may extend in small increments of time, the total time of the extendible interval, up to a maximum limit as timed by the maximum limit timer.

However, once the time gap between actuations of two successive vehicles of right-of-way traffic exceeds the allowable time gap, reset of the passage time is no longer permitted for the current interval and additional extension of the extendible interval terminates by operation of the extendible timer terminating unit. The remainder of the current timed passage is timed out from the termination of the timing of the allowable gap time, with the remainder of the passage time being equal to the mount of time the allowable gap has been reduced, at the time of termination of the last allowable gap time. At subseqiient termination of the passage time, the green period of that phase is terminated by the normal interval terminating unit.

The passage time may be adjusted as desired to allow an increment of sufficient green time for an actuating vehicle of right-of-way tr-afiic to enter the intersection once the vehicle has crossed the vehicle detector, but to terminate the green period thereafter if no additional actuations on the same phase occur within a foreshortened allowable gap time. If another vehicle actuates the vehicle detector of the same phase, prior to expiration of the foreshortened gap time, measure from the time of actuation of the preceding vehicle, the unexpired passage time is cancelled and another passage time increment is added. Thus, cancellation of unexpired passage time and timing of another passage time increment may continue until the gap time between two successive actuations exceeds the permitted gap time or the maximum permitted time of the extendible interval is exceeded-whichever first occurs.

If the gap time between two successive vehicle actuations exceeds the permitted gap time, or if no additional actuations occur, the extendible part of the timed interval is terminated by an extendible time terminating unit and the remainder of the passage time is timed, at the end of which the interval is terminated by a normal interval terminating unit. If successive time gaps between successive vehicle actuations do not exceed the permitted gap time and the time of the extendible part of the interval reaches the maximum permitted time of the interval, the interval will be terminated by the maximum limit timer, which automatically assures return of right of way without further tratfic actuation to the phase so terminated, as soon as the other phase right-of-way timing is completed.

An object is to provide an improved traffic control apparatus in which transfer of right-of-way from one traflic lane to the other traific lane of interfering lanes is determined by the time spacing. of right-of-way vehicles reaching or exceeding a time spacing limit which is reduced progressively with time in response to the first waiting vehicle on the interfering lane.

Another object is to provide an improved apparatus in which the charging circuit of the interval timer is electrically isolated from the trigger circuit of the timer so that operation of the trigger circuit does not aifect the condition of the charging circuit.

Other objects will become apparent from a reading of the specification in connection with the drawings in which:

FIG. 1 is a schematic diagram partly in block and partly in circuit form, representing one form of the present invention in which vehicle trailic at the intersection of two streets is controlled by actuation of traflic approaching the intersection;

FIG. 2 is a schematic circuit diagram of an electronic variable bias generating circuit;

- FIG. 3 is a schematic circuit diagram of the linearwith-time charging circuit;

FIG. 3a is a schematic circuit diagram of the extendible time terminating unit;

FIG. 3b is a schematic circuit diagram of the normal interval terminating unit;

FIG. 4 is a schematic circuit diagram of the maximum limit timing circuit;

5.. FIG. 6 is a graphic representation of variation of voltage between the positive terminal of the timing capacitor and ground with respect to time.

TWO PHASE STEPPING SWITCH CONTROL Referring to FIG. 1 in more detail one form of a twophase, full-actuated trafl'ic control system is illustrated with the trafiic controller controlling traffic signals controlling the intersection of two streets, A and B.

'It should be noted that although six banks of a multiposition stepping switch or line switch are illustrated, the illustrated components may represent a cyclic switching or cyclic actuating means or a step-by-step or a rotary cyclic cam contact means or any other multi-contact cyclic means providing equivalent functions.

The several banks of the stepping switch include eight positions, each with positions 1, 2 and 3 associated with one phase of the trafiic signal cycle, for example phase A and positions 5, 6 and 7 associated with the opposite phase of the trafiic signal cycle, for example phase B. During phase A right-of-way is withdrawn from phase B or street B and during phase B right-of-way is withdrawn from phase A or street A. Position 4 serves a dual purpose (note bank 6, position 4), position 4 may, with switch 300 open as illustrated, be associated with phase A and provide an all red timed interval, or other auxiliary phase A clearance interval, after the normal yellow or clearance interval of phase A, and, with switch 300 closed, position 4 may become associated with the phase B positions, becoming either a timed interval of the green period of phase B, timed in advance of the normal initial interval or a skip position, according to adjustment of the charging circuit as described below.

Position 8 is comparable to position 4, except that position 8 is associated with switch 301 and, with switch 301 open, as illustrated may be associated with phase B and provide an all red timed interval or other auxiliary phase B clearance interval after the normal yellow or clearance interval of phase B, and with switch 301 closed position 8 may become associated with the phase A positions, becoming either a timed interval of the phase A position, timed in advance of the normal phase A initial interval or a skip position according to adjustment of the charging circuit. It should be noted that the interval timed in position 4 is timed through position 4 of bank 1 and the interval timed in position 8 is timed through position 8 of bank 1.

Generally, the positions of bank I serve to complete part of the charging circuit for the R-C timing circuits used for timing the various timed intervals of the time increments of the right-oi-way period and clearance period. A positive direct current (DC) voltage, for example +75 volts D.C., may be employed. Between this positive D.C. potential and a substantially lower potential, as for example, ground zero, may be an impedance from which a desired potential between +75 volts DC. to

zero, may be picked off by an adjustable tap. Such picked ofi? potential may be used to bias a timing capacitor in an RC timing circuit, to time an interval in 'a well known manner, or to lift the timing capacitor above ground value to adjust the timing of the circuit by adjusting the amount of charge necessary to be applied to the timing capacitor at a controlled, preset rate so as to obtain a predetermined voltage charge in a desired time.

' It will be noted that the respective positions 1, 3, 4, 5, '7- and 8 of bank 1 individually provide individually adjustable, stable potential to block 302, LINEAR WITH TIME CHARGING CIRCUIT, via a wiper contact and lead 30.

The block 302 illustrated in circuit form in FIG. 3 includes a broken line box 31 which represents a means of coupling the wiper contact lead to the input to the rest of block 302.

- In positions 2 and 6 the output of block 303, VARI- ABLE BIAS GENERATOR, applied via line 20 is applied to the wiper of bank 1 and through the lead to the block 302.

Bank 2 serves-to illuminate indicator L1 in positions 1 and 5, indicating the initial interval of phase A, in position 1, and phase B, in position 5, is being timed. Further, indicator L2 is illuminated in positions 3 and 7 to indicate that the clearance interval of phase A, in posi tion 3, and phase B, in position 7, is being timed.

Positions 2 and 6 of bank 2 are included in individual parallel control circuits for the relay 304. Since the present controller is a full actuated controller, the controller must be called away from one phase to the other phase via actuation on the phase not then receiving rightof-way. This is a techniquethat is well known in the art or" traffic control and is employed in many full actuated controllers. It will be noted for example, that one control circuit for relay 304 includes position 2 of bank 2, which is a phase A position, and a normally closed contact 305b, of relay 305, the phase B detector relay. The other parallel control circuit for relay 304 includes position 6, which is a phase B position, and a normally closed contact 30615 of relay 306, the phase A detector relay.

Relay 304 may only be energized with the wiper contacts in position 2 or 6 and is employed to indicate the presence of a call for the phase not then being accorded right-of-way.

With the wipers of the line switches in contact with position 2, energization of the phase B detector relay 305, indicating a call for transfer of right-of-way to phase B, will open contact 30512 and deenergize relay 304. Similarly the wipers of the line switches in contact with position 6 energization of the phase A detector relay 306, indicating a call for transfer of right-of-way to phase A, will open contact 30612 and deenergize relay 304. In all positions other than 2 and 6 there is always an incomplete circuit so that relay 304 is deenergized in such other positions.

Inall positions of bank 3,with switches 307 and 303 closed, as illustrated, a ground connection is supplied via normally closed contact 304a of relay 304, via lead 40 to the block 309, MAXIMUM LIMIT TIMER, and via lead 39 to the block 3025 NORMAL INTERVAL TERMIN. (terminating). UNIT. The use of such ground connection will be more fully described in reference to the more complete description of FIG. 3b and FIG. 4. v

The switches 307 and 308 areknown in the art as coordination or. yield control switches. When the present controller is used in a coordinated system of traffic signal controllers the switches 307 and/or 308 may be adjusted to the up position and'the terminal 310 and/or terminal 311 may be connected to a master or other controller which may supply a ground connection only at a particular time and the present controller would be permitted to leave position 2 and/or 6 respectively only at the particular time in a background cycle, for example. This is a'feature that is well known in the art of traffic control and can be used to coordinate individual local controllers with a master controller in a master controlled trafiic control system.

- Bank 5 is associated, in positions 1 and 5 with the recall switches 312 and 313 respectively.

Position 2 and position 6 of bank 5 provide a ground connection via'normallyclosed contact 314a ofmo'tor magnet 314 through lead 37 to the block 302a EXTEND- IBLE TIME TERMIN. (terminating) UNIT.

Positions 3 and 7 supply a ground connection via the wiper contact to relay 304, which is one of the signal control relays. As described more fully below, the contacts of relay 304 cooperate with other contacts of other signal control relays to provide the yellow or clearance signal of phase A or phase B and the green or go signal of phase A or phase B.

The positions 4 and 8 are unconnected in the bank 5.

Bank 6 in positions 1, 2 and 3 provide a ground connection via the wiper contact to energize the relay 315 and positions 5, 6 and 7 provide a ground connection via MOTOR MAGNET OPERATION 'T he motor magnet 314 is representative of one means of sequentially stepping the wiper contacts of the line switch banks from'one position to the next succeeding position, all wipers being moved in unison. The motor magnet is normally denergized and may be energized manually by closure of push-button 318, which may be remotely located. Energization of the relay 319, found in FIG. 3b, will close the parallel circuit via contact 319a and also energize the motor magnet 314, while energization of relay 320, found in FIG. 4, will also close a third parallel energizing circuit via contacts 320a to-energize the motor magnet 314.

Along with the sequential stepping of the wipers of the line switch the motor magnet 314 also opens contact 314a, associated with positions 2 and 6 of bank and, closes contact 31412, found in FIG. 3 and 314a found in FIG. 4, each time the motor magnet is energized, the respective contacts returning to their normal positions upon deenergization of the motor magnet 314.

An indicating circuit coupled with relays 315 and 316 may be employed for indicating when the all red or other auxiliary interval, such as provided for in positions 4 and 8 with switches 300 and/or 301'open, are being timed.

INTERSECTION TRAFFIC SIGNAL CONTROL In the lower left part of FIG. 1 the signal control circuits, an intersection of two "roadways including St. A and St. B, with vehicle detectors A and A in St. A and vehicle detectors B and B in St. B, and associated trafiic signal lamps are represented. Along Street A, are three circles numbered 321A, 322A and 323A representing red, yellow and green lamps respectively. It should be understood that one side'of each represented lamp is to be assumed connected to ground to complete the signal control circuit; such ground connection has been omitted for convenience. Along the Street B, are three circles numbered 321B, 322B and 323B for red, yellow and green lamps respectively. It should also be understood that one side of each lamp is to be assumed connected to a ground connection to complete the control circuit.

With the relay 315 energized and relays 316 and 317 deenergized, such as in positions 1 and 2, the moving part of contact 31512 is pulled up so that a signal circuit is completed through the normally closed contact 3217b to illuminate the lamp 323A on Street A. Another signal circuit is completed through the normally closed contact 316b to illuminate the lamp 321B on Street B. Also indicator L4 is illuminated through the pulled-up contact 3151) to indicate the phase A part of the cycle is being shown.

In position 3, the relay 315 is maintained energized via bank 6, and the relay 317 is energized via bank 5. This relay combination maintains illumination of the lamp 321B on Street B. The lamp 323A on Street A is extinguished and the lamp 322A on Street A is illuminated via the operated contacts 315b and 317b.

In position 4 with switch 300 open, as illustrated, the signal control relays 315, 316 and 317 are all deenergized and both lamps 321A and 321B on each street are illuminated.

With switch 300 closed positions 4, 5 and 6 complete circuits to energize relay 316 while both relays 317 and 315 are deenergized. The moving arm of contact 316b is pulled up and the lamp 323B on Street B is illuminated the lamp 321A on Street A is illuminated through the normally closed contact 31512. Indicator lamp L5 is also illuminated and indicates that the phase B part of the cycle is being shown.

In position 7 relay 316 is maintained energized, via bank 6, and relay 317 is energized via the position 7 of bank 5. The relay 317 pulls up the moving arm of its contacts 317a and the lamp 323 B on Street B is extinproviding illumination of the lamp 323A on Street A and the lamp 321B on Street B.

It should be understood that the illustrated signal control circuits are presented in simplified form and interlocking to prevent illumination of two green signals simultaneously has been omitted for convenience.

On Street A two vehicle detectors A and A are represented as rectangles and are joined electrically at junction 50; It should be understood that the vehicle detectors employed in the present traffic control system may be of any of the well known type detectors sensitive to pressure, magnetism, microwave energy, heat or light, adapted to close a set of normally open contacts upon passage of a vehicle. 1

On Street B there are represented two vehicle detectors B and B which two vehicle detectors are electrically joined at junction60.

Above recall switch 312 is a junction 50, which also represents junction 50, the junction of detectors A and A. The set of Open contacts surrounded by a broken line box labeled A/A represents both vehicle detectors A and A.

Above recall switch 313 is a junction 60, which also represents junction 60, the junction of detectors B and B. The set of open contacts surrounded by a broken line box labeled B/B represents both vehicle detectors B and B.

Upon closure of the contacts of the detector A and/ or A, a circuit is completed to energize detector relay 306. With relay 306 energized the relay will pull up the moving arm at contact 306a and complete a holding circuit including lead 57 and normally closed contact 324a of relay 324 to ground. The relay 324 may be seen in FIG. 3a. A parallel holding circuit for the relay 306 may include normally closed contact 3156 to ground.

Energized relay 306 will drop out when contact 324a is Opened by energization of relay 324 and when relay 315 become-s energized and lifts the moving arm of its contact 3150 thus opening both described parallel holding circuits.

As will be described below with reference to FIG. 3a, relay 324 may be energized only in positions 2 and/or 6 so that if the relay 306- becomes energized the relay may hold in through contacts of relay 324 if the line switch is not in position 2; and when the lineswitch wipers do move into position 2 the relay 324 becomes energized and the relay 306 will drop out. In position 2 the relay 306 may be momentarily energized via closure of the detector contacts of the detectors A or A, but the holding circuits are open and energization of the detector relay 306 would last only so long as the vehicle detector contacts are closed.

Upon closure of the contacts of the detector B/B on Street B a circuit is completed to energize detector relay 305. With detector relay 305 energized the relay will pull up the moving arm at contact 305a and complete a holding circuit including the lead 67 and normally closed contact 324b of relay 324 to ground or through a'parallel circuit, when the moving arm of contact 3150 has been pulled up so as to provide a connection to,

9 ground. Energized relay 305 will drop out when contact 32411 is opened by energization of relay 324 and when relay 315 becomes deenergized and drops the moving arm of its contact 3150 and thus both parallel holding circuits are open.

The relay 324 becomes energized in the positions 2 and 6 so that if the relay 305 becomes energized, the relay may hold in through the normally closed contacts of relay 324 if the lineswitch is not in position 6; and when the lineswitch wipers do move into position 6 the holding circuit through the contact of relay 324 will open and the relay 305 will drop out. In position 6 the relay 305 may be momentarily energized via closure of the detector contacts B or B' but the holding circuit will not be completed and the energization of the detector relay 305 will last only so long as the vehicle detector contacts are closed.

Each detector relay, 306 and 305 has an associated indicator lamp L and L11 respectively, which lamp, when illuminated, indicates energization of its associated detector relay. Energization of a detector relay may result from actuation-of the associated vehicle detector, closure of the associated recall switch or termination of the last associated phase by the maximum limit timer thereby closing contact 3200.

Since the present controller includes two separate relay means to operate the motor magnet 314 it may be desired to know which relay means 319 of FIG. 3b, or 320 of FIG. 4, has operated the motor magnet 314. Thus indicator lamps L6 and L7 are provided to be illuminated upon closure of contact 31% and 320!) respectively.

Indicator lamp L8 and L9 are associated with positions 2 and 6 respectively of bank 5, in which positions the extendible intervals of phase A and phase B respectively, are timed. As previously described each extendible in terval is potentially extendible tentatively for another full passage time period when the gap time between two vehicle actuations is less than the allowed gap time. One total passage time includes a permitted gap time period plus the timed period of the remainder of the passage time, with the remainder of the passage time timed after expirationof one completed allowable gap time period. Actuations on the phase receiving right-of-way, occurring during timing of the allowed gap time may cancel the unexpired passage time and may begin the retiming of another passage time. If an allowed gap time is completely timed, without reset of the passage time, then the remainder of the passage time is timed to complete the passage time. passage time, unexpired passage time may not be cancelled by actuations occurring duringsuch time but actuation during the timing of the remainder of the passage time shall be remembered and cause the controller to return right-of-way to that phase after .completion of accord of right-of-way to the next place.

A transfer contact, 3250 selects between indicators L9 and L8 so that illumination of indicator lamp L9 indicates that an allowable gap time in position 2 or 6 is being timed while illumination of lamp L8 indicates that the remainder of the passage time is being timed in position 2 or 6. I

It may be desired to temporarily suspend or stop the timing of the controller either locally or remotely. Thus a relay and its control circuit may be provided, may be operated by closure of a switch manually operated or automatically operated either local or remotely located. When energized, the relay closes contacts 326b, 3260 and 326d located in FIG. 2, FIG. 3 and FIG. 4 respectively, to stop the timing of the timing circuits illustrated in the respective figures, the operation of which will be described below.

PHASE RECALL It will be noted that each recall switch 312 and 313 During timing of the remainder of the 10- includes four positions of a double poleswitch P l-P2. The description of switch 312 may serve for a description of switch 313 except that switch 312 is associated with phase A components and circuitry and switch 313 is associated with the corresponding phase B components and circuitry.

With the poles P1 and P2 of switch 312 in position 1, the output of block 302 through resistor 33 is grounded via lead 34, pole P2 of switch 312, position 1 of switch 312, lead 51 to position 1 of bank 5 so that with the wipers in position 1, and the poles P1-P2 in position 1, the normal interval timer of FIGS. 3 and 3b, is replaced with the timing performed by'the timer of FIG. 4, the maximum limit .timer during the timing of the initial interval only. 1

Further a circuit is completed upon closure of either normally closed contact 324a or the normally closed position of contact 315a from ground through either of the closed contacts via lead 57, lead 56, position 1 or 2 of switch 312, pole P1, lead 54 and 58 the coil of relay 306 to positive power. This circuit, available in positions 1 and 2 of the switch 312, provides an automatic recall of the phase A. The recall of phase A will occur when the wiper contacts of the lineswitch banks are in position 3. Upon energization the relay 306 will lock in through its holding circuit previously described.

The circuit associated with the switch 313, for recall of the phase B, is completed when the wiper contacts of the lineswitch banks are in position 7, with the ground connection being completed via contact 3245, lead 67, lead 66, position 1 or 2 of switch 313, pole P1 of switch 313, lead 64 and 68, the coil of relay 305 to positive power. This circuit, available in positions 1 and 2 of the switch 313 provides an automatic recall of the phase B. When the phase B clearance interval is being timed in position 7 relay 305 will be energized and will then lock in through its holding circuit previously described. It should be noted that either switch 312 or switch 313 may be adjusted independent of each other and with both switches 312 and 313 in position 1 or 2, (the switches are illustrated in position 1), each phase, A and B, will be provided with an automatic recall in the clearance period of the respective phase.

Thus with the switches 312 and 313 adjusted to recall the phases A and B respectively, operation of the controller may include automatic recall of both phases with vehicle extension of both phases individually responsive to actuation of vehicles in that particular phase during the norm-ally extendible interval.

With only one of the recall switches positioned for recall, right-of-way will be returned to its associated phase even in absence of vehicle actuation on that phase. The extendible interval of the recalled phase may still respond to actuation of its detector during timing ofthe extendible interval to extend the extendible interval to its maximum limit.

The position 2 of the respective switches dilfers from position 1 in that the circuit through the pole P2 is open so that the output of FIG. 3 through resistance 33 and line 34 is no longer grounded and the normal interval timer, the combined FIG. 3 and FIG. 3a may be used to time the initial intervals as described below.

1 With the switch 312 in position'3, automatic recall of the phase by the recall switch is not provided for.

Position 4 of the switch 312 pole P1 is connected-directly to ground and may be provided as a spring loaded position, for test purposes, so that the poles P1 and P2 would only stay on position 4 so long as they are held manually in the position. In position 4, the assumed spring loaded position, an automatic call would be put in via pole P-l lead 54, the coil of relay 306 to a positive power supply, regardless of the position in which the wipers of the several banks would be located at that time.

1 1 VARIABLE BIAS GENERATING UNIT Referring more particularly to FIG. 2, which may illustrate one form of circuitry represented by the box 303 in FIG. 1, the preferred form of electronic variable bias genera-ting unit is illustrated as one means of providing a direct current voltage output (via lead the amplitude of which increases progressively with time. The capacitor 71 is progressively charged, at a controlled rate and the charge on the capacitor is applied, via lead 20, as an output of the variable bias generating unit to position 2 and position 6 of bank 1 in FIG. 1.

Coordination among the wiper contact, and several relay contacts provides for holding the'variable bias generating unit in a quiescent state when the wiper contacts are in contact with positions other than 2 or 6 of the several banks of line switches.

The extendible vehicle interval of the phase A green period is timed in position 2 and the extendible vehicle interval of the phase B green period is timed in position 6. With the Wiper contacts in-position 2 and in position 6 the variable bias generating unit may be released from its quiescent state and begin to generate a DC. potential across the output capacitor with the output applied via lead 20 through either position 2 or position 6 of bank 1, depending upon the position in which the wiper contact is located, the wiper contact, lead 30, the coupling unit, represented by box 31, lead 32 to the lower part of timing capacitor 121 in FIG. 3. As will be more fully described with reference to FIG. 3, circuit 382 is an illustration of the preferred form of linear-with-time R-C charging circuit, the capacitor 121 serving as the timing capacitor.

Returning to the FIG. 2, the variable bias generating unit is provided with dual adjustments and selection between each set of adjustments is made by operation or non-operation of a relay contact. In the present form contacts of the relay 315, shown in FIG. 1, are employed to select between the sets of adjustments.

When the wiper contacts are in position 2 of the line switch banks, the controller is in phase A of the signal cycle and the relay 315, in FIG. 1, is energized. When the wiper contacts are in position 6 of the line switch banks, the controller is in phase B of the signal cycle and the relay 315 is deenergized. Thus transfer contacts of the relay 315 are employed as one way in which to select between phase A, position 2, and phase B, position 6.

The relay contact 315d selects between tap 73 and tap 74 each associated with the potential divider network 72. With relay 315 energized as with the wiper contacts in position 2, tap 73 is selected by closure of the upper contacts, of contact 315d, for phase A and with relay 315 deenergized, as with the wiper contacts in position 6, tap 74 is selected 'by closure of the lower contacts of contact 315d, for phase B. 7

Likewise contact 315e selects tap 75 by closure of its upper contacts in position 2 for phase A and selects tap 76 by closure of its lower contacts in position 6 for phase B. Both taps 75 and 76 are associated with the potential divider network 77. Further, contact 315 selects potentiorneter 78 by closure of its upper contacts and selects potentiometer 7 9 by closure of its lower contacts.

Thus adjustments at 73, 75 and 78 may be made, each associated with the same phase, phase A for example, and adjustments 74, 76 and 79 may be made, each associated with the alternate phase, phase B, for example.

The means used to select between phase A adjustments and phase B adjustment is one method that may be employed. Other methods as for example, employing additional line switch banks, when necessary, and use the positions 2 and 6 of the additional line switch banks to serve for selecting between phase A and phase B adjustments may be used in lieu of using relay AG contacts for such selections.

' As previously mentioned the circuitry in FIG. 2 is held in a quiescent state in certain parts of each phase ( positions 1, 3, 4, 5, 7 and '8 of the line switches) and may be I held in a quiescent state in position 2 and position 6.

As will be more fully described with reference to FIG.

3a, the relay 324 is held deenergized in positions 1, 3, 4, 5, 7 and 8, and may be held deenergized in position 2 and position 6. Thus, normally closed contact 3240 of relay 324 is employed as one method of holding the circuit of FIG. 2 in a quiescent state. When closed, the contact 3240 shunts across the capacitor 71 through low resistance 80. This circuit is also employed to discharge in FIG. 1, is employed to cooperate with the contact 324a, and also act as a safety circuit, tohold the variable bias generating unit in a quiescent state in position 2 and position 6 unless a call for the phase not then receiving right-of-way has been or is received, and if and when such call is received, relay 304 will become deenergized as previously described and release contact 30411 to its normally open condition and open the shunting circuit of the capacitor 71.

Normally open contact 32611 serves as another contact for shunting capacitor 71, and either establishing or maintaining a quiescent state for the circuit in FIG. 2 when desired.

Operation of the circuit of FIG. 2 is the same for the phase A components as for the phase B components except for the difference in adjustment of the respective components.

Typical operation of the circuit of FIG. 2 will now be described with the relay AG deenergized so that its normally closed contact are assumed closed as illustrated, and with contacts 326b, 3240 and 3041) open.

The tube 85, which may be one half of a commercially designated 12AU7, for example, is normally conducting, the amount of current passed being controlled by the grid to cathode bias which is relative to the potential applied to the grid 86 from junction 83.

A voltage divider network, represented by 72, with resistor elements between one DC. potential, for example volts, represented by a plus in a square, and a lower DC. potential, for example +21 volts, represented by a plus in a diamond may be employed, with variable taps 73 for phase A and 74 for phase B, used to tap off potentials which may be applied to the junction 83, through the closed contacts of contact 315d during phase A and phase B respectively.

The voltage value at tap 73 for phase A, and at 74, for phase B may be measured between junction 83 to ground across resistor 89 and may be adjusted so that the tube may be made to conduct at least at a desired rate or more.

The tube 85 is a cathode follower which establishes the voltage at the cathode of tube 90 at a point established by tap 74 on network 72.

It should be noted that tube 85 is not essential to the operation of this circuit. If tube 85 is omitted, sufiicient current must flow through network 72 so that variations in current of tube 90 do not cause any substantial change in the voltage at tap 74. The cathode of tube 9%) would be connected directly to contact 315d under these conditions.

The cathode 91 of tube 90 which may be one half of a commercially designated 12AX7, for example is connected to junction 8-7 so that the cathode 88 of tube 85 and 91 of tube 90 are at the same voltage level.

The plate 84 of tube 85 is connected directly to the +250 volt D.C. source while the plate 93 of tube 90 is connected to the +250 volt D.C. source through a resistor 95. Thus the plate potential at 84 is higher than the plate potential at 93 under corresponding conditions.

The current path through the tube 90 followsfrom the supply, represented by a plus in a circle, resistor 95, junction 94, plate 93, through tube 90 to cathode 91, junction 37 and through a cathode resistor to ground. The voltage drop across resistor 95 increases as the current flow through tube 90 increases. A parallel voltage divider circuit also includes the same .current supply, resistor 95, junction 94, constant voltage drop lamp 96, junction 105, resistors 97, 98 and 99, diode 101, the closed contacts of contact 315e, tap 76 of voltage divider network 77 to ground. It will be noted that grid 92 of tube 90 is con nected to the voltage divider circuit between resistor 98 and 99 thus any change in voltage drop across resistor 95 will result in a change in potential on the grid 92. Also adjustment of the tap 75, for phase A and 76, for phase B will change the potential at the grid 92.

A change in the grid 92 potential may change the bias of tube 90 and may effect the amount of conduction through tube 90.

Thus the amount of conduction through tube 90 is a result of the balancing of the efiect of the voltage drop across resistor 95, the setting of tap 75 for phase A and 76 for phase B, each of which effect the potential on grid 92 which effects the bias of tube'90 which controls the amount of conduction through tube 90.

The voltage divider circuit and its efiect on tube 90 when tap 75 or 76 is readjusted becomes important since adjustment of tap 75, for phase A and 76 for phase B sets the passage time of the extendible interval. The passage time is set by adjusting the base or lowest voltage level of the curve seen in FIGS. and 6 referred to as the BIAS curve. The position of taps 75,'for phase A and 76, for phase B also determine the voltage value above ground at which the capacitor 71 will be held.

As the voltage in the voltage divider circuit changes the voltage value at junction 105 will also change. The charging circuit for capacitor 71 includes the source of supply, resistor 95, junction94, constant voltage drop lamp 96, junction 105, diode 106, resistor 107 the closed contacts of contact 315 potentiometer 78 for phase A and potentiometer 79, for phase B, junction 109 capacitor 71, lead 110, the closed contacts of contact 3152, tap 75, for phase A and tap 76 for phase B part of the resistor of network 77 to ground.

The potentiometers 78 and 79 are rate adjustments, which control the rate at which the capacitor 71 will be charged so that the adjustment of potentiometers 78 for phase A and 79 for phase B'determine the slope of the curve BIAS in FIGS. 5 and 6 and thus determine the rate of reduction of gap time or the amount of time it will take to reduce the gap time from maximum gap to minimum gap.

Thus since the passage timeadjustment, taps 75 and 76, sets the lowest voltage value on capacitor 71 as shown by the BIAS curve in FIGS. 5 and 6 and the time to reduce from maximum gap time to minimum gap times sets the rate of change of the available voltage, adjustment of the taps 75 for phase A and 76 for phase B may change the the voltage value at junction 105. Change in the voltage value at junction 105 changes the applied voltage through the potentiometers 78 and 79 so that the time to reduce from maximum gap time will remain the same and need not be recalibrated or adjusted in the vent of a change in the gap time differential.

The amount of passage time is proportional to the differential between the minimum or base voltage level of capacitor 71 (indicated, for example, as plus 80 volts in FIGS. 5 and 6) and the predetermined flash or trigger voltage of the timing circuit (indicated, for example as +160 volts in FIGS. 5 and 6). l

a The potentiometers 78 and 79 are used to adjust to the desired time to reduce from the maximum allowed gap time to the minimum allowed gap time. The maximum allowed gap time depends upon the minimum or base voltage level of capacitor 71 (and thus the setting of t'aps 75 and 76 for phase A and phase B respectively), and the preset flash or trigger voltage of the timing circuit.

The minimum allowed gap time depends upon the setting of taps 73 and 74 on network 72 for phase A and phase B respectively, and the same preset flash or trigger voltage level.

The time to reduce from maximum allowed gap time to minimum allowed gap time is independent of the differential between the maximum and minimum allowed gap time. Since the accumulation of charge applied to a capacitor, such as 71,'is a function of the setting of potentiometer 78 or 79 (the rate control component) and the magnitude of the voltage applied to the rate control components, and it is desired to have the capacitor 71 charge from a low value to a high value in a given time regardless of the difference between these values, the voltage applied to the rate control potentiometers must be varied through a range of values, being raised as the diiferential between these two settings increases.

Each time a passage time is readjusted by adjustment of tap 75 or 76 for phase A or phase B, the maximum allowed gap time for that phase is changed and the differential between the maximum allowed gap time and the minimum allowed gap time for that phase is changed.-

The difierential between maximum and minimum gap times may also be changed by changing the minimum allowed gap time as by adjustment of tap 73 and 74 for phase A and phase B respectively.

In order to maintain the time to reduce from maximum allowed gap time to minimum allowed gap time as preset by the potentiometers 78 and 79, without readjustment of the potentiometers each time the diiierential between gap times is changed, the voltage values across the several parts of the voltage divider circuit, including resistors 95, 97, 98, 99 and tap 75 or 76 and lamp 96, and particularly at junction 105, bettween lamp 96 and resistor 97 are changed, so that the amount of charge applied to the capacitor 71 through the rate controlling potentiometers will be readjusted, according to the change in voltage value so that the differential between the maximum and minimum allowed gap time will be traversed over the same period of time.

When the assage time is increased (thereby increasing the maximum gap time) and the minimum gap time remains the same, the voltage at junction is increased accordingly so that the then increased difierential between maximum and minimum gap times may be traversed over the same period of time. When the passage time is decreased (thereby decreasing the maximum gap time) and the minimum gap time remains the same, the voltage at the junction 105 is decreased so that the then decreased differential between the maximum and minimum gap time may be traversed over the same period of time.

The change in voltage at junction 105, in the voltage divider circuit, results from a change in resistance in the voltage divider circuit by adjustment of the taps 75 for phase A and 76 for phase B, so that when the passage time is readjusted, the value of the voltage at junction 105 is automatically readjusted so that the magnitude of voltage applied through the rate controlling potentiometers is changed and the amount of voltage charge accumulated on the capacitor 71 over the same period of time is changed so that the new difierential is traversed over the same period of time as preset.

As is well known to those skilled in the art, the voltage across a capacitor being charged through a resistor increases rapidly at first, and then slower and slower as the capacitor voltage approaches the supply voltage. Since the change in voltage becomes very slow after a period of time equalling about 3 times the product of the capacity and the charging resistance (a product commonly called the time constant) and it is desirable when handling traffic, to cause the allowable gap to be reduced in a much more linear manner, it is necessary to apply a voltage to the rate control component which is some multiple of the difference between the maximum and minimum desired values. The degree of multiplication determines the amount of change-in-rate obtained. The

higher this multiplication, the smaller part of a time constant the capacitor will require to reach the desired charge level (voltage) and the more uniform will be the rate of change, hence the more linearly will the gap be reduced. This multiplication is performed by the tube 90 and related components resistors 95, 97, 93 and 99 and lamp 96.

Since the constant voltage drop lamp 96 which may be a neon lamp, for example, requires more voltage to illuminate the lamp than to maintain the lamp illuminated, an illumination sustaining circuit, including a source of power, resistor 95, junction 94, lamp 96 and high resistance 102 to ground, keeps the lamp 96 illuminated in the event that the voltage across the divider circuit is insuflicient to sustain illumination of the lamp 96.

Therefore, when released from a quiescent state, the capacitor 71 begins to charge from a preset base voltage level, as determined by the setting of tap 75'or 76, at a rate controlled by potentiometer 78 or 79 with the potential across the capacitor '71 as measured from junction 109 to ground applied, via line to bank 1 positions 2 in phase A, and 6 in phase B, the wiper contact, lead to the box 302, shown in circuit form in FIG. 3, and applied to the timing capacitor 121 in FIG. 3 to bias the capacitor 121 with a voltage above ground.

CHARGING CIRCUIT Referring now to FIG. 3, the linear-with-time charging circuit is illustrated in circuit form and may illustrate the circuitry found in the box 302 in FIG. 1.

Generally, the linear-with-time charging circuit includes a timing capacitor 121 and timing resistors 122 and 123,

of which resistor 123 may be adjusted to adjust the rate variable resistance 123, resistor 122, switch S-1, to ca-' pacitor 121. The charging circuit may also include the lead 32 and resistor 116 to a ground connection. The function of switch S-1 and the shunted circuitry will be later described. The switch 8-1 is here assumed closed, as illustrated.

The cathode follower 115 may be the electrical coupling between the variable bias generating unit of FIG. 2 and the linear-with-time charging unit in FIG. 3 with the grid 117 controlled by the output of FIG. 2 and the bias charge applied to timing capacitor 121 from the cathode of tube 115 via lead 32.

As the charge from the cathode circuit of tube 124 is applied through the timing resistance 122/123 to capacitor 121 the accumulating charge on the capacitor is applied to the control grid 133 of tube 125 and conduction through tube 125 increases. As conduction through tube 125 increases the cathode potential at junction 134 increases. The potential at junction 134 is applied through resistor 33 to contact 324d and, depending upon the position of the moving arm of contact 324d via lead 36 to the normal interval timer, represented by box 3112b in FIG. 1, and illustrated in circuit form in FIG. 312 or via lead to the extendible time terminating unit, represented by box 392a in FIG. 1 and illustrated in circuit form in FIG. 3a.

The voltage at junction 135 which is at a fixed value above the voltage at junction 134 by an amount equal to the voltage drop across the constant voltage drop lamps 126/127 is applied to the grid of tube 124, which tube is a cathode follower. As the voltage applied to the grid of tube 124 increases, conduction through the tube 124 increasesresulting in increased voltageat junction 130.

The voltage at junction .130 is"an amount above the voltage at junction 134 and the voltage at junction 134 is 7 i=5 essentially the same as the voltage on capacitor 121 as measured between junction 12% and ground.

The voltage charge on timing capacitor 121 is applied from junction through the timing resistors 122 and 123 andas the voltage at junction 130 increases the rate of charge on capacitor 121 increases thus increasing the conduction of tube 125 and'the voltage at junction 134. As the voltage at junction 134 increases the voltage at junction 135 increases to cause tube 124 to conduct more heavily thus increasing the voltage at junction 130. Thus the voltage value at junction 130 is progressively increased so that the capacitor 121 is charged substantially linearly with time.

With the relay contact, 324d in its normally closed condition, asillustrated in the interconnections between FIG. 3 and FIGS. 3a and 3b, the voltage at junction 134 may be applied through lead 36 to junction 141, the potential at junction 141 is applied to the grid 146 of triode 145. Resistor 142 and capacitor 143 connected in parallel between-junction 141 and ground serve as an electrical filter.

The timer illustrated in FIG. 3b may be in the form of the electronic timing circuit taught by Peter C. Brockett in his US. Patent No. 2,964,625, issued December 13, 1960. Thus the triode 145 is normally non-conducting and the triode is normally conducting. The voltage at cathode 151 of tube 150 resulting from conduction of tube 150 is impressed on the cathode 147 of tube 145 by virtue of the connection at junction 153. The potential applied to grid 152 of tube 150 is picked-off at point 157 of a potential divider including the coil of relay 319, resistor 155 and resistor 156. Junction 158 may be at ground potential, when lead 39, which is connected via contact 364a to the wiper contact of bank 3 (FIG. 1), is grounded or may be at a higher potential when the ground connection is broken (contact 304a open).

When the connection to ground via lead 39 is broken, the resistor 159 is included in the potential divider along with resistors 155 and 156 so that the potential at point 157 is sufiiciently high to maintain tube 150 conducting very heavily. When lead 39 is connected to ground, the resistor 159 is by-passed and no longer forms a part of the potential divider. Thus the potential divider at junction 157 and on grid 152 would be reduced but still hold tube 150 normally conducting.

With the reduced potential at junction 157, the potential at junction 134 in FIG. 3, may be increased thus increasing the potential at junction 141, FIG. 3b, and

therefore increase the potential applied to grid 146 of tube 145.

When the potential on grid of tube 145 becomes sufficiently high to overcome the potential on cathode 147, tube 145 begins to draw plate current and increase the voltage drop across the coil of relay 319. With increased voltage drop across coil 319 the potential at junction 157 is reduced resulting in tube 150 becoming non-conducting and forcing tube 145 to conduct heavily and operate the relay 319.

The timed intervals of positions 1, 3, 4, 5, 7 and 8 are timed by cooperation of the linear-With-time charging circuit of FIG. 3 and the normal interval timer of FIG. 3b with the lead 39 of FIG. 3b connected to ground thus excluding the resistor 159 from the voltage divider circuit of the interval timer and with the variable bias generating unit disconnected from the electrical coupling box 31 and replaced by a selected fixed bias, as more fully described below.

With the wiper contacts of the several banks of lineswitches in position 2 or position 6, the relay 324, in FIG. 3a may be energized so long as relay 325 in FIG. 3a remains deenergized.

Relay 325 is normally deenergized and in such condition its contact 325ais normally open, and 325i) is normally closed. Contact 3250, associated with indicator lamps L8 and L9, in FIG. 1 is also in its normally closed condition so that indicator lamp L9 is illuminated. With contact 3 b closed, relay 324 is energized and contacts 324a and 324b, in the holding circuit of detector relays 306 and 305 respectively, in FIG. 1, are open. Contact 3240, in FIG. 2, is open and thus holds open one of the parallel shunting circuits for capacitor 71. Contact 324d, in the connecting circuitry network between FIG. 3 and FIGS. 3a and 3b is in its pulled-up condition and connects the output from the linear-with-time charging circuit with lead 35, into the extendible time terminating unit of FIG. 3a. Contact 324a is closed to prepare a discharge circuit, including the upper contacts of 315g and contact 3062 in phase A and the lower contacts of 315g and contact 305e in phase A, for wash down of the charge on the timing capacitor 121 in FIG. 3. The described discharge circuit is used to cancel the unexpired passage time and affect retiming of the passage time in the extendible part of the vehicle interval timed in position 2 for phase A and 6 for phase B.

EXTENSION TIME TERMINATING UNIT The extension time terminating unit illustrated in FIG. 3:: includes a ground control circuit for grounding the output of the linear-with-time charging circuit when relay 364 is energized so as to operate contact 3040 to its closed position and the relay 324 is energized so as to operate contact 324d to connect lead with the output of the charging circuit. A filter including a resistor and capacitor in parallel is connected between the input into FIG. 3a and ground. A triod-e 170 with a relay 325 connected between the power supply and the anode 171 of tube 170 is also included in FIG. 3a.

The input into FIG. 3a is connected to the grid 172 of tube 170 so that when an output is applied from FIG. 3 to the input of FIG. 3a and contact 3040 is open, the input is applied to the grid 172.

The cathode 173 is illustrated as connected to a potential somewhat above ground, represented by a plus in a circle in a square, so that when there is suflicient charge applied to grid 172, sufiicient plate current will flow to energize relay 325. Relay 325 will close its contact 3250 and complete a holding circuit for the relay 325 which may be completed via lead 38, position 2 or 6 of bank 4, the wiper contact in position 2 or 6 to ground. Contact 32% will be operated to open the energizing circuit for the relay 324 and contact 3250 (FIG. 1) will be operated to extinguish indicator lamp L9 and illuminate indicator lamp L8.

MAXIMUM LIMIT TIMING CIRCUIT Referring now to FIG. 4, a schematic circuit diagram of an electronic timer, which may illustrate the maximum timer represented by box 309 in FIG. 1 is shown with the lead 40, which is shown connected to contact 304a in FIG. 1.

As described in reference to FIG. 3b, the lead 40, which may be the same as or a parallel lead to, lead 39 is con nected to contact 304a and is connected to ground so as to effectively ground junction 181 when the wiper contacts are in positions 1, 3, 4, 5, 7 and 8 and thus exclude resistor 182 from a potential divider circuit including the coil of relay 320, resistors 183 and 184 between a positive potential and ground. When ground is applied to junction 181 the potential at junction 185, between resistors 183 and 184 is lowered so as to hold the tube 190 conducting and hold tube 195 non-conducting but permit the tube 195 to become conducting when the potential applied to grid 196 is sufiiciently high.

. In positions 2 and 6 the relay 304 may be energized and open its contact 304a, this opens the circuit so that junction 181 is no longer at ground potential and adds the resistance of resistor 182 to the potential divider. The addition of this resistance, which may be of the order to 1.5 megohms, for example, lifts the potential at junction 185 and thus the potential on grid 191 so as to maintain 18 tube 190 conductive and maintain tube 195 non-conductive regardless of the potential applied to the grid 196, within circuit limits.

The tubes 195 and 190 in FIG. 4 are comparable to tubes and respectively in FIG. 3b and the junctions 181 and in FIG. 4 are comparable to junctions 158 and 157 respectively in FIG. 3b.

The timing capacitor 201 in FIG. 4 is comparable to timing capacitor 121 in FIG. 3 and tubes 205 and 206 in FIG. 4 are comparable to tubes 124 and 125 respectively in FIG. 3.

The tubes 205 and 206 of FIG. 4 are interconnected, similar to that also illustrated in FIG. 3 so as to provide a linear-with-time charge to capacitor 201.

The contact 315b is used to select between phase A adjustment, tap 211, and phase B adjustment, tap 212, on the potential divider network 213.

The resistor 215 and adjustable resistor 216 are timing resistors with 216 used to adjust the rate of chage through the closed contact 304d, from the cathode voltage at junction 217 of tube 205.

The taps 211 and 212 are used to adjust the charging time by biasing, with a steady potential, the timing capacitor 201. This is similar to the operation of the timing circuit of the combined FIGS. 3 and 3b when the lineswitch wiper contacts are in positions other than 2 or 6 except that in the combined FIGS. 3 and 3b the potential applied from any one tap of the potential divider associated with bank 1 in FIG. 1 is applied through the electrical coupling, box 31.

The timer illustrated in FIG. 4 is employed for several purposes. The timer serves as the maximum limit timer for the extendiole vehicle interval of any phase. With the switch 312 or 313 in position 1, the timer serves as the timer for the initial interval of phase A or phase B respectively replacing the normal initial interval timer. At other times the timer serves as a safety timer which may terminate any interval in the event that the normal timing circuit fails to operate and terminate the interval in the normal manner.

Contact 314a is provided to complete a discharge cirouit of timing capacitor 2411 upon its closure. Contact 314c is closed by operation of motor magnet 314 so that contact 3140 is closed during the stepping operation of the wiper contacts. Thus at the beginning of each interval the capacitor 20d is substantially discharged to its lowest Value.

Contact 304d controls completion of the charging circuit for maximum timing capacitor 201.

In position 2 and position 6 relay 304 may be energized if there is no call or demand for transfer of right-of-way to phase B or phase A respectively. If relay 304 is energized contact 304d is open and capacitor 261 will not begin to charge. Further, as previously described, contact 2564b in FIG. 2, is closed to hold the variable bias generating unit in a quiescent state and contact 3040 in FIG. 3a, is closed to ground the output voltage applied to the extension time terminating unit by the linear-with-time charging circuit, FIG. 3, and contact 304a is open thus opening the ground connection to the junction 181 in FIG. 4 and junction 158 in FIG. 3b which efifects the trigger circuit as described below for FIG. 4 and described above for FIG. 3b.

Thus with relay 304 energized the maximum limit timing circuit capacitor rests in a dischanged condition, prepared to start timing a maximum limit time when a demand for transfer of right-ofway, which may open the energizing circuit for relay 304 and cause the relay to become decnergized, is received. The variable bias generating unit is also held in a quiescent state, prepared to start generating a bias control voltage when relay 3% becomes deenergized. With relay 304 energized, the linear-with-time changing circuit in FIG. 3 is timing the minimum time that the iwiper contacts must remain in position 2 or 6. This minimum time is measured from the time at which the wiper contacts reach position 2 or 6 or from the end of a subsequent actuation of the vehicle detector on phase A or phase B respectively.

If the wiper contacts move from position 1 to; position 2 or from position to position 6 to eifect timing of the extendible vehicle interval of I phase A or phase B respectively and there is a demand for transfer of right-of-Way, it is desired to limit the time of the extendi-ble interval to no more than a predetermined maximum limit, and for such timing the maxi-mum limit timer is employed and simultaneous initiation of the normal extendible interval time and the maximum limit timer is desired.

If there is a demand for transfer of right-oflway, the relay 304 will be deenergized or maintained deenergized as the wiper contacts move into position 2 or 6, according to when the demand for transfer of right-of-Way is received and operation of the maximum limit timer is initiated.

. If there is no demand for transfer of right-o flway, there is noneed to limit the time period of the exte'ndible intervaland the maximum limit timer is held inoperative. This is accomplished by energization of relay 304, as explained.

Let it be assumed that a demand for transfer of rightof-Way has been received prior to advance of the wiper contacts into position 2 or 6 so that the relay 304 is maintained deenengized. With relay 304 deenergized contact 304a is closed to place ground via lead 40 on junction 181 of FIG. 4 and via lead 39 on junction 158 in FIG. 3b. Contact 30'4b is opentopermit operation of the variable bias generating unit, FIG. 2, contact 30 4c in FIG. 3a is open to breakthe grounding of the output 'of the linearwith-time charging circuit and contact 304d in FIG. 4 is closed to permit operation of the maximum limit timer. This occurs as soon as the wiper contacts move into position 2 or 6, and thus simultaneous initiation of the maximum limit timer and the nonmal'extendible interval timer is obtained. I

As soon as the wiper contacts move into position 2, torexam-ple, to. time the phase A extendible vehicle inter- Wal, capacitor 201 begins to charge from the voltage ap plied at junction 217 through" contact 304d, adjustable resistor 216, timing resistor 2-15 to the capacitor 201. The

circuit is completed through the upper contact of 3150 (relay 315 is energized in phase A); tap 211' to ground.'

The. charge applied to capacitor 201 is applied over the stable ,biasimpressed' on capacitor 201' from the'netiwork 213, tap 211, the upper contacts of 3=15h to capacitor 201. i I

The charging cunve of the maximum limit timing circu-i-tis represented as the linear curvev 226, MAXIMUM LIMIT TIMING; in FIG. 5.

At the same time as timingcapacitor 201 begins to charge the capacitor 121 begins to -charge linearly with the charge applied upon a progressively increasing bias,

as controlled by the increasing charge on capacitor 71.

The voltage on'capa'citor 121 as measured between junction 120 and ground no w'follows the curve represented by 228, RESULTANT TOTAL VOLTAGE, in FIG. 5 or FIG. 6.

If the change on capacitor 121 increases so that the tube 170 in FIG. 3a passessufiicient current to operate relay 325 and subsequently'operates thetrig ger circuit to operate relay 319, the interval timed in position 2 willterminate by operation of the normal interval terminating unit, FIG. 3b. A-t termination of the intenval by opera- 7 that the wiper contacts may now be maintained in position 2 Will be timed by the maximum limit timer.

As the charge on capacitor 201 increases'the increased potential is applied to grid 207 ofitube 206. This causes tube 206 to conduct more heavily which increases the on the capacitor effects the amount of voltage at junction 217, thus tube characteristics and'component values are such that the charge on capacitor 201 increases linearlywith-time.

The voltage at junction 210 is impressed on grid 196 of tube 195. When the potential on grid 196 becomes sufliciently high, tube 195 will pass current and force tube to cut-off. Conduction of tube will cause operation of relay 320.

Energization of relay 320 closes contacts 320a in FIG. 1 to energize motor magnet 314; may close a contact to illuminate an indicator lamp thereby indicating that the interval was terminated by operation of the maximum limit timer; closes contact 3200 which causes energization of relay 306 and automatically puts in a call or demand for return of right-of-way to phase A after serving phase B. Relay 306 is energized by a circuit from ground through contact 320c, the upper contacts of 3151', lead 58, the c oilof relay 306 to positivepower. If the last described interval timed had been the extendible vehicle interval of phase B (position 6) then the relay 315 would have been deenergized and the stable bias impressed on capacitor 201 would have been impressedvia tap 212 and the lower contacts of 3151:. Further upon operation of relay 320 closure of contact 3200 would have caused energization of relay 305 for recall of right-of-way to phase B after phase A has been served. Relay 305 would have been, energized by a circuit completed from ground through contact 320e, the lower contacts of 315i, lead 68, the coil of relay. 305

to positive power.

Upon energization of motor magnet 314 by closure of contact 320a, contacts 314b and 314c are closed to discharge capacitors 121 and 201 respectively. Contact 314a is opened to cause deenergization of relay 324. which closed contact 324a and causes discharge of capacitor 71.

With capacitor 201 discharged, conduction. through tube 206 is reduced thus reducing the voltage at junction.210 and the potential applied to grid 196. Conduction through tube .195 ceases causing deenergization.

of relay 320. andrestoring tube 190 to a conductor state; The contactsof relay 320 are reversed to their normal condition and motor magnet 314 is deenergized and advances the wiper contacts to'po sition 3.

Thus the extendible interval of any phase maybe terminated by operation of the maximum limit timer with automatic recall of right-of-way after the next phase has been served.

NO TRAFFIC CONDITION If there .is no traffic on either phase or street both detector relays 306, and 305 willz remain deenergized and the minimum time .during which the wiper contacts must remain in position 2 or 6 is timed. Since the variable bias generating unit is held in a quiescent state, a minimum stable bias is applied to the timing capacitor 121.

This stable bias is the maximum allowed gap level shown so that the output of 302 thelinear-with-time charging 304a, 304b, 304c and 304d to their normal conditions,-

as illustrated in the several drawings.

The maximum limit timer FIG. 4 will begin to charge timing capacitor 201; the variable bias generating unit, FIG. 2, will begin to increase the bias on timing capacitor 121 via increase of the charge on capacitor 71 and the output of the linear-with-time charging circuit will be applied to the grid 172 of tube 170 since the ground connection via contact 3040 will be open.

Tube 170 will pass sufiicient current to operate relay 325. Energized relay 325 will open its contact 32511 and deenergize relay 324. Deenergized relay 324 will reverse its contact 324d and the output of the linear-with-time charging circuit will be applied via lead 36 to the grid 146 of tube 145 of the normal interval terminating unit.

Tube 145, will begin to conduct and cause tube 150 to cease conduction and tube 145 will operate relay 319.

Energization of relay 319 etfects termination of the in-.

TRANSFER OF RIGHT OF WAY Returning to the time of advance into position 2 or 6 without a demand for transfer of right-of-way assume now that there is a succession of vehicles along the roadway receiving right-of-way. As previously described the maximum limit timing circuit will be held inoperative, waiting for an actuation demanding transfer of rightofway, timing capacitor 121 will be charged linearly between successive actuations.

Assuming now that phase A has right-of-way, with each actuation of the detector A or A the detector relay 306 will be operated for substantially the length of time the contacts A or A are closed. During operation of relay 306 contact 306e will be closed to complete a discharge circuit to discharge the linearly applied charge on capacitor 121 to the base bias voltage value. The capacitor 121 will begin to recharge linearly when contact 306a opens.

This action will be repeated for each actuation of vehicle detector A or A so long as no demand for transfer of right-of-way, via actuation of vehicle detector B or B, is received. I

Assume now, that after severalactuations of detectors A or A which reset capacitor 121, that the linearly applied charge on capacitor 121 is now at a value above the base bias voltage but below the value at which tube 170 will pass current to operate relay 325 and an actuation of detector B or B is received.

Closure of the contacts of detector B or B will complete a circuit to energize relay 305 from ground through contact B or B, junction 60, leads 65, 64 and 68, the coil of relay 305 to positive power. Relay 305 will pull in and open its contact 30512 and drop out relay 304. Relay 305 will also lock-in through its holding circuit as previously described, through contact 305a and 3150.

With relay 304 deenergi'zed its contact 304a closes and places ground on junctions 158 in FIG. 3b and 181 in FIG. 4 so that the trigger circuits in FIGS. 3b and 4 respectively may operate. Contact 304c is opened so that the output of FIG. 3 may be applied to the grid 172 of tube 170 in FIG. 3a and contact 30417 is opened to release the variable bias generating circuit from a quiescent state. Contact 304d is closed and the timing capaci- 22 for 201 of'FIG. '4 begins to charge and time the'maximum' limit time that the phase'A green may now be extended.

It should be noted that prior to a demandfor transfer of right-of-way being'prese'nt when the controller is in an extendible vehicle'interval there is no time limit that the controller may remain in position 2 or 6. Also, prior to demand for transfer of right-of-way'there is no varying bias on timing capacitor 121which,as described below, reduces the allowed gaptirne as thebias'increases. The charging of capacitor 121 occurs over a steady bias and the voltage change is linear with time.

Returning to the last assumed condition, the capacitor 121 continues to be charged linearly but now is also impressed with a bias that is'inci'easing in value. This changes the rate at which the voltage between ground and point at the upper side of the capacitorwill increase.

Now assume an actuationo'ccurs onphase A. Again the linear charge on capacitor 121 will be discharged, as previously described, but the bias, which has now increased above the base bias voltage level remains unaffected by the actuation. "After actuationpf A or A ceases the linear charge is again applied to the capacitor 121 over the now increased 'biaslevel, I

Additionalsubsequent actuationof the B or B detector have no additional effect on the controller due to the detector relay being held energized.

I Additional subsequent actuations of the A or A detector will extend the time of the "extendible interval, as previously described, by discharge of the linear charge on the capacitor, but will not affect the progressively increasing bias voltage. I

When the voltage on capacitor121 increases sufficiently to cause relay to pass current relay 325 operates and prepares the timing circuit for termination of the interval.

It should be noted that termination of the extendible interval by the normal interval terminating unit occurs in two steps; first operationof the extendible time terminating unit, which is a preparatory step, which does not afiect the charge on the capacitor but may reduce the bias on the capacitor if the bias is in excess of the base bias value and the second step, operation of the normal interval terminating unit. These two steps are indicated by illu mination of the indicator lamps L9 and L8 respectively. Operation of relay 325 causes drop out of relay 324 which closes cont-acts to open the detector operated discharge circuit, reduce the bias to its base value by discharge of capacitor 71 and transfers the output of the linear-with-time charging "circuit from FIG. 3a to FIG. 3b.

With reduction of the bias on capacitor 121 the charge remains the same but the voltage between ground and point 120 at the upper side of the capacitor is reduced by the amount of reduction of the bias, The capacitor is now charged linearly without possibility of reset by detector actnations since contact 324a 'is now open. When the linear charge. or voltage onthe capacitor 121 is sufficient, the normal interval terminating unit will operate to termin ate the interval, during which the capacitor 121 is discharged, and the wiper contact-s arefadvanced to position 3. Advance of the wiper contacts to position 3 opens the connection between. the variable bias generating unit and the electrical couplingarid connects the stable bias,,fr'om 25a of network for example to the electrical coupling, which may p'rdvide' a diif erent bias value from the base bias of the variable bias generating unit. p h V 1 I g It should be noted that rate of charge of the capacitor 121 may be on a. constant slope asset by a calibration adjustment, by adjustment of adjustable resistor 123 for example. This calibration may remain as-adjusted and the time period of the non-extendible intervals may be set by adjusting the appropriate tap such as tap 25a for the position 3, phase A clearance interval, to provide a desired value of bias voltage to be impressed on capaci- 23 tor 121, which may set the desired time period of the interval to be timed. A time period is determined 'by the slope of the charge curve and the dilferential between the base bias voltage on the capacitor and trigger voltage of the trigger circuit which terminates the interval.

It should also be understood that the bias voltage applied to -capacitor,121 may vary from one interval to the next according to adjustment of the associated tap with the interval to ,be timed as the wiper contacts advance from one position'to-the next in their step by step cycle.

CHARGING Ass DIS-CHARGING CURVES Referring now to FIG. -5, a graphic representation of the various normal charging and discharging curves is illustrated with the'vertical component representing voltage, and the horizontal component representing time.

The curves represent the normal, complete charging and discharging that may occur during an extendible interval or any one phase with the value of the charge represented by the vari-ous curves measured on the capacitor 121', from junction 120 to ground.

It is assumed that the time zero starts simultaneously with the start of the extendible interval (at the same time the wiper contacts move into con-tact with position 2 or position 6) and there is a call or demand for transfer of right-of-way.

- The low voltage value on the vertical scale is represented to be at 80 volts above the zero or ground volt age level while the high value of volts is represented to be at 160 volts above ground on a graduated scale marked off in 10 volt segments. It should be understoodthat the voltage values, although practical for the charging and timing circuits in my improved controller, merely represent voltage values and the line 232, labeled MAXIMUM ALLOWABLE GAP LEVEL, represented to be at 80 volts, may be set at some other voltage value, if desired. The position of the line 232, with respect to-gr-ound, at the voltage scale is adjusted by the setting oftap 75 for phase A and tap 76 for phase B on the network 77, seen in FIG. 2, which sets the base voltage for low voltage level on the capacitor 71 in FIG. 2, which in turn determines the conductivity of tube 115 in FIG. 3 which applies the desired bias voltage value by the lead 32 to timing capacitor 121. The voltage level to which the line 232 is adjusted is therefore the lowest voltage value to which the capacitor 121 may be reduced. The value, on the volts scale at which .line 232 is set, determines the passage time, which is thediiferential between line 232 and 230, timed on the charging curve 227, the LINEAR CHARGE VOLTAGE curve and also determines the maximum allowable gap time, which is the differential between line 232 and line 236), timed on the, charging curve 228, .the RESULTANT TOTAL VOLTAGE chargingcurveQ p The position of line 230, labeled FLASH OR'TRIG- GER VOLTAGE on the voltage scale, is determined by the voltage that may be, measured on the capacitor 121, at which the tube 171, in FIG. 3a, will flash or trigger and the tube 145 in FIG. 3b, will trigger. It should be noted that the position of line 230 on the scale of volts is not necessarily the flash or trigger voltage level of the trigger circuit but rather the voltage on the capacitor 121 which will cause the tube 125 of FIG; 3 to conduct andprovide suflicientvoltage output from junction 134 inFIG. -3 to cause the tube 171 in FIG. 3a and the tube 145 in FIGL' 3b to" trigger and pass current when the voltage output from junction 134 is'applie'd to the respective tubes.

The set-ting of line 231, the MINIMUM ALLOW- ABLE GAP LEVEL, on the volts 'scalei'determines the minimum allowable gap time. The amount of time of the minimum allowable gap is the traversed time,..n1eas- 24 ured on the curve 228, RESULTANT TOTAL VOLT- AGE between the line 231 and 230.

a The setting of the line 231 is determined by the highest value of the charge applied to the timing capacitor 121 via lead 32 from the cathode circuit of the tube 115. The value of the highest cathode voltage of the tube 115 so applied togcapacitor 121, is determined by the amount of conduction of tube 115, which is determined by the value of'the potential applied to the grid 117 of tube 115 which is the highest charge on capacitor 71, as determined by the setting of tap 73 forphase A and tap 74 for phase B. Thus tap 73 in FIG. 2, may be used to set the minimum allowed gap for phase A and tap 73in FIG. 2, maybe used to set the minimum allowed gap for phase B.

The differential between line 231 and-232 is the differential between the maximum allowable gap time and the minimum allowable gap time. The rate at whichthe difierential between line 231 and line 232 will be traversed in time, represented by the curve 225, BIAS VOLTAGE, is determined by the setting of the potentiometer 78 for phase A and 7? for phase B shown in FIG.

2. Thus the potentiometers '78 in FIG. 2 may be used to determine and adjust the time to reduce from maximum allowed gap to minimum allowed gap for phase A and the potentiometer 79 in FIG. 2, may be used to set the time to reduce from maximum allowed gap to minimum allowed gap time in phase B. r The angle of the line 227, LINEAR CHARGE VOLT- AGE is adjusted by the setting of the adjustable resistor 123 in FIG. 3, which is a calibration adjustment. passage time may be measured by the traversed time between 1ine232 and 230 on curve 227. Since taps and 76 adjust the position of the line 232 for phase A and phase B respectively then taps 75 and 76 respectively may be used to adjust the passage time for phase A and phase B respectively.

The curve 225, BIAS VOLTAGE represents the bias voltage applied to the capacitor 121, from the electrical coupling tube cathode, via lead 32, the lowest value, represented at time zero, is setby the base voltage or low voltage level on thecapacitor 71 in FIG. 2, and sets the minimum amount of conduction of tube 115 and thus the value of the lowest voltage applied to the capacitor 121 via lead 32 in FIG. 3. As the charge on capacitor 71, in FIG. 2 varies, conduction of tube 115 in FIG. 3 varies proportionally and the bias voltage applied ,tocapacitor 121 in FIG. 3 via lead 32 varies according to the amount of conduction of tube 115. V

The amount of linear charge applied to capacitor 121 through the timing resistor 122 and adjustable resistor 123 from junction 13 0 of the cathode circuit of tube'124 in FIG. 3 is represented by the line 227, LINEAR CHARGE V-OLTAGE. The curve 228, RESULTANT TOTAL VOLTAGE, is the summation of the curves 225 and 227 and represents the value of the linear charge plus the value of the bias voltage. It was previously described how the capacitor 121 could be biased simultaneously by the voltage applied via lead 32 which is represented by curve 225 and charged by the voltage applied from junction 130 through the timing resistors 122 and 123 which is along the curve represented by line 227 in FIG. 5. The line 228 may represent the charge on capacitor 121 measured from junction to ground. It was also described how either the bias voltage, along the curve 225 or the voltage charge; along the curve 227, could be individually reduced to their lowestvalue without eflecting the accumulated charge along the other curve. Thus if for example the capacitor 121 was charged along the curve 228 from the line 232 to the line 230, the FLASH OR TRIGGER VOLTAGE and the trigger circuit in FIG, 3a was operated to reduce the volt-' age bias along the curve 225 to'its lowest level, as for example as indicated by the broken line 225, the charge on the capacitor would be reduced to the value of the remain:

ing charge, or to the line 227 as indicated by the broken line 228'. By continuing to charge along the linear curve 227 the charge on the capacitor 121 could be again increased to the line 230 at which time the trigger circuit in FIG. 3b may be operated terminating the interval and reducing the voltage charge, represented by curve 227' to its lowest level thereby completely discharging the capacitor 121 to its lowest level or to line 232 in preparation for the next interval.

The curve 226, MAXIMUM LIMIT TIMING represents the charging or voltage curve of the maximum limit timer, FIG. 4, and is represented as starting from a common base voltage for convenience. It should be noted that the curve 226 may start at a common voltage level or at another voltage level, according to the setting of the adjustment 211 and 212.

The horizontal component, representing time, is sealed in seconds and graduated in five second units, marked off on line 232 for convenience. This time scale is used for convenience and merely represents one time scale that could be used when associated with the voltage values used herein.

GRAPHICAL SHOWING OF TIMING CAPACITOR OPERATION Referring now to FIG. 6, a graph illustrating curves which represent the charging and biasing and discharging of the charge and bias of the timing capacitor 121, as measured between junction 12% and ground, which may occur during the extendible interval, is presented to illustrate the cooperative effect within the composite timing circuit.

The vertical component of the graph in FIG. 6 is identical to the vertical component of the graph in FIG. 5, both in character and scale,

The horizontal component of the graph in FIG. 6 is similar to the horizontal component of the graph in FIG. with respect to character but the scale of time value in FIG. 6 is one half again larger than the scale of time in FIG. 5.

The position of the lines 230, 231 and 232 on the vertical scale in FIG. 6 is similar to the position of the identical lines in FIG. 5. However since the horizontal scale of FIG. 6 is larger than that of FIG. 5 the contour of the voltage charging and discharging curves differ between the two graphs to some degree, although corresponding voltage curves are labeled similarly, between the two figures.

For simplification of the drawing, the voltage curve 226, MAXIMUM LIMIT TIMING, has been deleted from FIG. 6 although it is to be understood that the voltage curve would begin at time zero with the beginning of the other voltage curves illustrated in FIG, 6.

It should be assumed that the controller has been operating for a substantial period of time and that there is a demand for transfer of right-of-way. Further assume that the wiper contacts of the line switch move from the position in which the initial interval is timed (position 1 or 5) into the position in which the extendible interval is timed (position 2 or 6) with the timing capacitor 121 completely reduced to its lowest value, here assumed to be +80 volts.

The broken line curve 227 illustrates the linear change of voltage as the capacitor is charged and the broken line curve 225 represents the bias voltage applied, each of which are applied to the timing capacitor 121, as described. The solid line 228 represents the resultant voltage which is the sum of the lines 225 and 227.

The charges applied to timing capacitor 121 accumulate along the curve 228, the bias applied from box '31 via lead 32 to the bottom of timing capacitor .121, in FIG. 3 and the charge from the cathode circuit of tube 124 from junction 13% via adjustable resistor 123 and timing resistor 122 to the top of timing capacitor 121.

After about 5 seconds, as arbitrarily'assumed, one of the detectorsof the street receiving right-of-way is actuated. This, as previously described, causes energization of the associated-detector relay, and the energized relay causes closure of its normally open contacts, in particular contact 306e or 3ti5e.

If right-of-way is displayed on Street A, relay 315 will be energized and contact 315g will be closed in its up position and actuation of detector A or A will cause energization of relay 306 which will close 306a.

For clarity, let it be assumed that the right-of-way is now accorded to trafiic on Street B so that relay 315 is deenergized and contact 3153 is closed in its down position. Further since the moving traflic is.on Street B the detectors actuated by the moving traflic will be B and/0r B thus detector relay 305 will be energized and contact 3%)5e will be closed each time there is an actuation of detector B or B.

Closure of contact 305:: will complete the prepared discharge circuit including contact 3242 and the lower contact 315g discharging capacitor 121, as indicated by curve 228 from point A1 to curve 225. Upon cessation of actuation relay 395 becomes deenergized and the discharge circuit opens and capacitor 121 begins to recharge. At this point in time the bias applied to capacitor 121 has not been reduced but is now higher than it was at time zero.

The charging of capacitor 121 begins along curve 228-1.

If an actuation of detector B or B has not occurred before the curve 228 reaches line 230, such as shown in FIG. 5 the flash or trigger voltage would have been reached and the BIAS VOLTAGE would have been removed, such as illustrated in FIG. 5 by broken line 225' and 228. This measured time, although referred to as the maximum gap time may only be a measure of gap time in actual traffic if an actuation on B or 13' occurs simultaneously with the start of the interval, otherwise, it is the time during which the first actuation of the interval must occur in order to extend the interval.

The curve 228-1 illustrates the charging curve of capacitor 121 after actuation Al and assumes that a second actuation on B or B occurs at time A2. This again discharges the capacitor to curve 225.

Above the graph the line 327 represents the time of the actual gap time between actuations while the line 328 represents the time of the permitted gap time. The line 329 represents the time of the remainder of the passage time, as measured in time from the point at which curve 228-1 including its projection, in broken line form reaches line 230, and drops along the line 22S-1 due to the reduction of the BIAS curve at 225-1 to the point at which the biasing curve 227-1, intersects with line 230. The passage time is the time included in the time 323 plus time 329.

With cessation of actuation at A2 the voltage on capacitor 121 rises along curve 228-2 withthe permitted gap time indicated along line 331'). It is now assumed that the gap time between actuations is greater than the permitted gap time and that the voltage curve 228-2 reaches the line 230. This operates the terminating unit of the extendible portion of the extendible interval, FIG. 3a. Relay 325 operates to drop out relay 324 which opens its contact 324a and opens the discharge circuit FIG. 3, closes contact 324a to discharge capacitor 71 in FIG. 2 and thus reduce the current flow through the cathode follower in box 31 and thus reduce the curve 225 along line 225' to its lowest level. This reduces the resultant total voltage along line 228'-2 to the curve 227-2 which then charges linearly to the line 230. The line 331 represents the remainder of the passage time while the total passage time actually measured from actuation A2 to termination of the passage time is measured by the lines labeled 339 plus 331.

Termination of the interval timed in the position re- 237 sults in complete. discharge of timing capacitor 121 to its lowest level along line 227'-2. 1

If an actuation should occur before the curve 228-2 ,reaches line 230, that is within thepermitted gap time, the

capacitor voltage would be reducedv again to the BIAS curve 225,. Additional subsequent timely actuations that occur within the permitted gap time (which is being progressively reduced with the rise of curve 225) cancel the unexpired gap time and remainder of the passage time. Time of the passage time will begin all over again, however, with each successive cancellation of the unexpired passage time, the gap time is further reduced and It should be noted that, as more readily seen in FIG. 1, positions 1, 2 and 3-of the line switches are comparable to positions 5, 6 and 7 respectively except that positions '1, 2 and 3 are associated with phase A (Street A herein) and positions 5, 6 and 7 are associated with phase B (Street B herein). With such arrangement the network 21. supplies a voltage for positions 1 and with tap 24a connected to position land .ta-p 24b connected to position 5 with position 1 used as part of the timing circuit for the initial, non-extendible interval, of phase A and position 5 used as part of the timing circuit for the initial,

non-extendible interval, of phase B. The taps 24a and 24b may be independently adjusted so that each initial interval of the respective phases may be independently timed and at different time intervals, if desired. 7

Network 22 supplies a voltage for positions 3 and 7 'via tap 25a, for phase A and tap 25b for phase B re spectively. Positions 3 and 7 are used as part of the timing circuit for the clearance interval, of phase A and phase B respectively. i I

The network 23 supplies a voltage for positions 4 and 8 via taps 26a and 261) respectively.

The voltage applied to positions 1 and 5 via taps 24a and 24b respectively from network 21 are substantially stable and individually control the cathode follower in box 31 to conduct at a substantially steady rate orvalue, thus providing a steady or stable bias on the timing capacitor in box 302. This bias controls the amount of charge necessary to be applied to the capacitor, 'at a predetermined rate to arrive at a predetermined value which will provide a predetermined amount of conduction of the tubes controlled by the timing capacitor in box 302.

EFFECT OF SUBSTANTIAL TRAFFIC Let is now be assumed that the recall switches 312 and 313 are both adjusted to be in the position #3 in which there is no recall by the respective switches and the controlleris operated as a full traffic actuated controller.

Further assume that there is a substantial amount of trafiic on both streets, A and B, and that the wiper contacts of the controller have just been advanced from position 8 to position 1.

Relay 315 is energized and relays 317 and 316' are deenergized so that the green signal 323A on Street A is illuminated and the red signal 321B on Street B is illuminated. Both detector relays 306 and 305 are here assumed energized, both being locked-in via their respective holding circuit.

The relayv 324 in box 302a is deenergized so'that the contact 324d is in its normally closed lower position so that box 302 is connected to box 302b co ntact 324b in 28 box 303 is closed'thus shunting capacitor 71 and holding the circuitry in box 303 in a quiescent state and contact 324@ in box 302 is open to provide against reset of timing capacitor 121.

The potential tapped off network 21 via tap 24a is applied to position 1 of bank 1 and to the wiper contact and, via lead 30 to the cathode follower in box 31, which functions as previously described, and thence via lead 32 to the box 302 to be applied to the timing capacitor 121 as a stable bias, thus serving to control the amount of charge needed, the charge being supplied at a constant rate, to increase the potential on the capacitor121 so as to cause tube 125 to conduct sufficiently heavy to cause the tubes 150 and of box 302b to reverse their conductive and non-conductive condition respectively, and operate relay 319.

Energized relay 319 closes its normally open contacts 319a and, completes a circuit to energize motor magnet 314. A second relay contact'may also illuminate an indicator lamp indicating that the interval is now terminating by action of the interval timer relay 319.

Motor magnet 314 opens its normally closed contact 314a, FIG. 1, and closes its normallyopen contacts 31412, in box 302 (FIG. 3), and 314s in box 309' (FIG. 4). Closure of contact 31412 discharges capacitor 121 as previously described and contact 3140 discharges capacitor 201 as previously described.

Discharge of capacitor 121 reduces the potential on grid 133 of tube 125 and tube 125.conduets less heavily. Thus the cathode voltage of tube 125 is.reduced and.the output applied to grid-146 of. tube 145 in box 3021) is reducedand tube 145 becomes non-conductive thus causing relay 319 to become deenergized.

Deenergized relay 319 opens itscontacts 319a dropping out motor magnet 314. When motor magnet 314. became energized it engaged a toothed gear (not shown) andupon deenergization the gear is rotatedto move the wiper contacts to the next position, position 2.

Position 2 is. the extendible vehicle interval timing position. When the wiper contacts arrive in position 2 the output of box 303 (FIG. 2) is connected via lead 20, to position 2 of bank 1, the wiper. contact, lead:30, box 31, lead 32 to box 302. Thusthe variable bias generating unit, FIG. 2 is connected to the linear-with-time charging circuit, FIG. 3.

Indicator lamp L1 is extinguished and the relay. 304, which could be energized in position 2'ofbank2, is held deenergized due to energization of relay 305, holding contact305b' open. With relay 304 deenergized contact 304a remains closed and junction 181 in FIG. 4 and junc- 'tion 158in FIG. 3b are both' at ground potential.

The, relay 324 in FIG. 3a is now energized through its ground connection from the wiper contact of bank 5, position 2, contact 314a, lead 37 to box 302a, FIG. 3a, normally closed-contact 1325b coil of relay 324 to positive power. Relay 324 opens its contacts 324a, 3924b and 324e, closes its-contact 324e and reverses its contact 324d the latter contact connecting the output of box 302 via resistor 33 to lead 35 and thus to the grid of tube 170.

Contact 3244;, FIG. 1, opens and breaks the holding circuit for relay 306. Contact 324a, FIG. 2 opens'and breaks theshunting circuit for capacitor 71 and capacitor 71 beg'insto charge. Contact 324e, FIG. 3 closes and prepares a reset or discharge circuit for timing capacitor 121 which may be completed, upon actuation of (the vehicle detector.A or A and energization of relay 306 which will close contact 306e, through the closed upper contacts 315g, through alow resistance to the bottom of capacitor 121.

At the same time capacitor 201 of FIG. 4, the maxi; mum limit timer, also begins tocharge and time. the maximum time that the'wiper contacts may remain in position 2.

Asdescribed relative to FIG.,3, thecharge on-the ca- 29 pacitor may, during certain of the timing of position 2 be discharged but the bias voltage is retained. This provides for an increasingly reduced extension time increment, as described.

The time interval the wiper contacts are permitted to remain in position 2 may terminate either by the maximum timer operation of relay 320 or by the normal Operation of relay 325 followed by operation of relay 319.

As previously described the motor magnet 314 may be energized via action of relay 319 in FIG. 3b or relay 320 in FIG. 4. If the relay 320 is energized and acts to terminate the interval the contact 320a will be closed which will complete an energizing circuit for the relay 306 as previously described.

EFFECT ON TRAFFIC LAGGING Assuming that there is a sufficient gap in trafiic on Street A so that the potential across the timing capacitor 121 increases so that tube 125 in FIG. 3, passes current sufiiciently heavy to provide sufficiently high voltage to cause tube 170, in FIG. 3a to pass current to cause energization of relay 325, relay 325 will be energized and lock-in through its holding contact 325a, lead 38, position 2 of bank 4 to ground. Energized relay 325 opens its contact 3251) and relay 324 becomes deener'gized. Contacts 324a,. 324k and 324C are released and closed. Closure of contact 324a completes the holding circuit for relay 396 through its own holding contact 366a. Closure of contact 324b completes a parallel holding circuit for relay 305. Closure of contact 3240 completes a shunting circuit for the capacitor 71 in FIG. 2 and discharges the capacitor thus reducing the bias voltage being applied to the timing capacitor 121 in FIG. 3 to its lowest value. Contact 324d is reversed so that the output of tube 125 in FIG. 3 is connected to lead 36 so that the output voltage from tube 125 in FIG. 3 is applied to the grid 146 of tube 145 in FIG. 3b.

It should be noted that the closure of contact 3240 reduced the bias on the capacitor 121 in FIG. 3 by discharging the capacitor 71 in FIG. 2 and now holds the variable bias generating circuit in a quiescent state but that capacitor 121 from junction 130 continues to be charged, with the bias, if any on the capacitor 121, held stable in contrast to the varying bias. Thus the potential across the capacitor 121 hasbeen reduced to the value of the linear-with-time charge since the variable bias voltage has been removed and the capacitor 121 is now charged linearly to the point where the tube 125 passes sufiicient current to provide suflicient output voltage to cause the tube 145 to begin to conduct and energize the relay 319.

Operation of relay 319 will cause energization of motor magnet 314 which causes discharge of capacitor 121 in FIG. 3, via closed contact 31411 and discharge of capacitor 201 in FIG. 4 via closed contact 314a. Upon deenergization, motor magnet 314 advances the wiper contacts to .the next position, position 3 Referring momentarily to bank 3 in'FIG. l, particularly the switch 307, it is assumed that the switch 307 is closed as illustrated. Closure of the switch 307 provides a ground connection to the box 309 and 302b so that the junction 181 in box 309 and junction 158 in FIG. 3b are at ground. If it is desired to control when the interval timed in position 2 may terminate, then the switch 307 may be positioned so as to connect with the upper terminal 310. The terminal 314.? may be connected to a master or other controller and may supply a ground connection at a desired time so that the controller may move out of position 2 at a desired time.

Along these lines the terminal 332 extending from positions 2 and 6 in bank may be used for connection to either 'or'both- terminals 310 and 311 of another controller so that one controller may be used as amaster controller for other controllers in a traffic control system.

Referring again to FIG. 3 the purpose of switch S1 3% will now be described. It may be desired to temporarily increase the time of the clearance interval of any one phase, under certain conditions.

1 With switch S-1 closed as illustrated the circuitry network including resistor 240 and contacts 3176, 306 and 305 and shunted and temporary extension of any clearance interval is not permitted.

With switch S1 open the resistance of the resistor 240 may be added to the resistance of the combined resistors 122 and 123 under certain conditions, and only in a clearance interval. Since the relay 317 is energized only in a clearance interval, position 3 and 7 for example, the contact 317e is closed in all other positions so that in all other positions the resistor 240 is by passed by the shunting circuit through closed contact 317e.

In order that the controller move into a clearance interval there must be a demand for transfer of right-ofway so that the detector relay of the phase calling for right-of-way is energized, thus its contact either 306 or 305 will be open. Also in any clearance interval relay 317 is energized and contact 317:: is open. Thus in a clearance interval for phase A, for example contact 317:: will be open and contact 365i will be open. If an actuation of A or A occurs after operation of the 'extendible time terminating unit and before termination of the clearance'interval or. if the phase A green period is terminated by operation of the maximum limit timer relay 306 will become energized and the contact 306 will open to open the network shunting resistor 240 and insert the resistor 240 into the timing circuit. This increase of the timing resistance will temporarily increase the time period of the current clearance interval.

Temporary increase of the time period of the clearance interval under corresponding conditions may occur during phase B, position 7.

It will be appreciated that while the apparatus disclosed herein represents the preferred embodiment of my invention modification in the design and arrangement of the several parts and substitution of equivalent parts and circuits may be made in manner known to those skilled in the art without departing from the spirit of the invention as defined by the claims.

I claim:

1. In a traffic control system for interfering traffic lanes having traffic actuatable means for the respective lanes, right of way signals and a timing mechanism for controlling said signals to time successive period of accord of right of way successively to said lanes, said timing mechanism including a capacitor, circuit means for charging said capacitor linearly with time subject to time reset by discharge of said capacitor, means for so discharging said capacitor in response to actuation of said traflic actuatable means for the lane having right of way, second circuit means for adding an aiding bias voltage in series with said timing capacitor and progressively increasing with time from an initial bias voltage value, first responsive means coupled to said capacitor and bias to be controlled by the total voltage across said capacitor and said bias for preventing further such discharge of said capacitor by said traflic actuated discharge means and for resetting said second circuit means to maintain its initial bias voltage value in response to a predetermined total voltage to permit said capacitor to continue charging from the resulting lower bias and second responsive means controlled by said total voltage for terminating said right-ofway signal period in response to substantially the same predetermined total voltage resulting from said continued charging of said capacitor when said second responsive means is coupled to said capacitor and bias to be so controlled, and means coupled to said first responsive means to be controlled by operation thereof to so couple second responsive means to said capacitor and bias.

2. In a trafiic control system for accord of right of way in succession to intersecting traffic lanes in response to traflic actuation on the respective traflic lanes, tramc actuatable means individual to the respective traffic lanes,

right'of way indicating means and a timing mechanism for timing periods of accord of right of way by said indicating means to the individual lanes respectively, said timing mechanism including a resistance-capacitor circuit in which the voltage from one side of'the capacitor to a reference is the sum of the voltage from thecharge on the capacitor plus a capacitor bias voltage, a trigger circuit coupled to said zcapacitortobe controlledby said voltage from said one side of said capacitor to said reference, to be'oper-ated at a predetermined said voltage, means for charging said capaeitor at a linear predetermined time rate, means for varying the bias voltage pro-t gressively with timeduringaccord of right of way in one lane. to determine a time period therefor according.

to the charging timeof the capacitor between the voltage levelof the bias and said predetermined voltage level,

3. Ina traffic signal control system for intersecting trafiic lanes for extending right-of-way in one of said lanes in response to closely spaced vehicle actuations therein and for initiatinga transfer of rightvof-way from said one lane toanother said lane when the time gap between successive vehicle actuations in said one lane exceeds an allowable time gap, and for providing a further continua: tion of right-of-Way in said one lane fora brief time period after-said initiation of transfer to provide a passage time for the last prior actuating vehicle to reach the intersection, a resistance capacitance based timing circuit for providing the said gap timing and passage timing, said circuit comprising a capacitor, means including a resistance and a voltage source having a constant differential relation to the voltage on said capacitor for charging said capacitor at a linear time rate, means for discharging said capacitor,

in response to actuationby vehicles having the right-ofway in said one lane, means for providing an aiding bias voltage in series with said capacitorand for increasing said aiding bias voltage gradually with time while said right-of-way period is being so extended, first voltage -responsivemeans coupled to said bias means and said capacitor to be controlled by the total voltage across said eapac;

itor and said bias voltage for operating at a predetermined. said -total volta ge,; the dfiterence between: said predeter mined total voltage and said bias voltage representing said allowable gap, means coupled to said first voltage responsive-means'to be operated inresponse to said operation thereof to prevent further vehicle actuated discharge of said capacitor and to substantially eliminate said bias voltage whereby said capacitor can continue to charge toward said predetermined total voltage, second responsive means for operating inresponse -to said total voltage again reaching substantially said predetermined-valueas said capacitor continues to charge when said seeond responsive means is coupledto said capacitor, means con trolled. by the first mentioned responsive means so operat};

ing to couplesaid secondresponsive means'to said capacitor tobe so controlled by the said total voltage after said bias voltage has been so substantially eliminated and said capacitor continues to charge, and. means operated by said operation of said vsecond responsive ,meansto terminate the accord of right-of-way to saidone lane.

4., A combination as in claim 3 andincludinga cathode follower coupled to said capacitor and said. bias voltage means to becontrolled by the said total voltage'across said capacitor and said; aiding bias for so controlling said respective responsive means.

5. A combination as in claim 3 and in which said means providing said bias voltage includes atcathode follower whose output is connected in series with said capacitor,- and in which said means for gradually increasing said bias includes a second resistance-capacitance timing circuit:

havingla slowly varying charge on its capacitor whichis coupled to the input of said cathode follower to controlsaid output to so increase said bias.

' 6. In a trafiic control system for extending right-of-way on one traflic phase and preventing transfer to another trafiic phaseby reset of a timer by actuation by successive on said capacitor from an initial value: progressively toward a different final value :for. said timer, means for returning the chargev on said capacitor substantially to said.

initial value in response to vehicleactuation on said,one phase having right-ofway-to so reset said timer, means-for. providing a bias voltage. in series with said capacitor, a

cathode follower having said biasvvoitage and said capac i-,

tor coupled to its input, means for progressively varying said bias 'voltage frorn an initial level toward another.level with time, a first voltage responsive device coupled to the.

output of said cathode follower to be operated in response to the charge on said capacitor reaching a predetermined level to provide a predetermined voltage to said input, and asecond voltage-responsive device adapted to be coupled to the output of said cathode. follower to be operated at a higher levcl-ofcharge of said capacitor thansaid first responsive device. to.provide a predetermined voltage to,

said input, means for restoring said bias voltage tosaid initial level inresponse to operation-of said first voltage responsive device and means for socoupling said second voltage responsivedevice to said cathode follower in response to said operation of saidfirst voltage responsive device, whereby the same capacitor may .provide twodifferent time functions reset from the same .traffic actuation related to said right-of-way extension. I a

7. In a traificcontrol system for intersectingtraific lanes including stop? and go signals for the respective lanes,. traific actuatable means for the respective lanes and means for, controlling such signalsto accord right-of-way in succession to .the respective lanes in response, to actuation of. the respective said tralfic actuatable means, said signal controlling means including timing means for, timing a display period of a igo signal toone lane and y a stop" signal to the other lane, said timing means including .a capacitor, means for varying the charge on said capacitor from an initial value progressively at a predetermined time rate toward a different final value, for timing, biasing means for providing a voltagebias in series withsaidlcapacitor with'respect to a reference,- reset circuit means for resetting the charge on said capacitor substantially to said initial value to reset said timing in response to actuation of the traflic actuatable means of said one lane having said go signal to provide a part of saidgo{ signal period extendible by traffic therein, means for respondingto a predetermined voltage on said capacitor and said bias with respect to said reference to terminate said extendible part of said go signal period,,and means for varying said bias progressively at a predetermined time rate from a first voltagelvaluetoward a second voltage value in a direction to reduce the difference between said bias voltage and-said predetermined voltage to progressively 'reduce the time period over which said charge is so varied for such timing.

8. 'A combination as in claim 7yand in which bias varying means includes means for so varying said bias in the go signal periodfor said one lane in response to actuation of the traffic actuated means of the other lane having a .stop signal. I

9. A combination as in claim. land in which said means'for terminating the extendible .part'of said signal display period includesmeans for preventing further said resetting of the chargeon said capacitor by said reset circuit means, means forresetting said, bias to and maintainingsaid bias at substantially saidfirst voltage valuev to permit said progressive variation of saidicharge on said. capacitor to continuefor timing a non-extendiblepart of said go signal display period following said extendible part, and said timing means including, second responsive means for responding to said predetermined tvoltage as said progressive variation of charge of said capacitorcontinues to said predetermined voltage for. terminating said second part Of said signal display period in response to 33 34 the voltage on said capacitor in such continued charge References Cited by the Examiner variation reaching said predetermined voltage when said UNITED STATES PATENTS second responsive means is coupled to said capacitor t0 2 883 643 4/1959 Du 340 37 soresod,ad nsoeratd'reson toert' 1 11 p n n ma p e m p Se 0 p a 10m 2,925,583 2/1960 Jeiiers s 340-37 of said first responsive means to said predetermined voit- 5 age to so couple said second responsive means to said T D capacitor upon said reset of said bias substantially to its REIL Prlmary Exammer said first value. THOMAS B. HABECKER, Examiner.

Claims (1)

1. IN A TRAFFIC CONTROL SYSTEM FOR INTERFERING TRAFFIC LANES HAVING TRAFFIC ACTUATABLE MEANS FOR THE RESPECTIVE LANES, RIGHT OF WAY SIGNALS AND TIMING MECHANISM FOR CONTROLLING SAID SIGNALS TO TIME SUCCESSIVE PERIOD OF ACCORD OF RIGHT OF AWAY SUCCESSIVELY TO SAID LANES, SAID TIMING MECHANISM INCLUDING A CAPACITOR, CIRCUIT MEANS FOR CHARGING SAID CAPACITOR LINEARLY WITH TIME SUBJECT TO TIME RESET BY DISCHARGE OF SAID CAPACITOR, MEANS FOR SO DISCHARGING SAID CAPACITOR IN RESPONSE TO ACTUATION OF SAID TRAFFIC ACTUATABLE MEANS FOR THE LANE HAVING RIGHT OF WAY, SECOND CIRCUIT MEANS FOR ADDING AN AIDING BIAS VOLTAGE IN SERIES REPLICA OF THE TRANSMITTED VIBRATORY SINGAL AND THE ELECWITH TIME FROM AN INITIAL BIAS VOLTAGE VALUE, FIRST RESPONSIVE MEANS COUPLED TO SAID CAPACITOR AND BIAS TO BE CONTROLLED BY THE TOTAL VOLTAGE ACROSS SAID CAPACITOR AND SAID BIAS FOR PREVENTING FURTHER SUCH DISCHARGE OF SAID CAPACITOR BY SAID TRAFFIC ACTUATED DISCHARGE MEANS AND FOR RESETTING SAID SECOND CIRCUIT MEANS TO MAINTAIN ITS INITIAL BIAS VOLTAGE VALUE IN RESPONSE TO A PREDETERMINED TOTAL VOLTAGE TO PERMIT SAID CAPACITOR TO CONTINUE CHARGING FROM THE RESULTING LOWER BIAS AND SECOND RESPONSIVE MEANS CONTROLLED BY SAID TOTAL VOLTAGE FOR TERMINATING SAID RIGHT-OFWAY SIGNAL PERIOD IN RESPONSE TO SUBSTANTIALLY THE SAME PREDETERMINED TOTAL VOLTAGE RESULTING FROM SAID CONTINUED CHARGING OF SAID CAPACITOR WHEN SAID SECOND RESPONSIVE MEANS IS COUPLED TO SAID CAPACITOR AND BIAS TO BE SO CONTROLLED, AND MEANS COUPLED TO SAID FIRST RESPONSIVE MEANS TO BE CONTROLLED BY OPERATION THEREOF TO SO COUPLE SECOND RESPONSIVE MEANS TO SAID CAPACITOR AND BIAS.

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