US3522581A

US3522581A - Timed decision load control system

Info

Publication number: US3522581A
Application number: US586232A
Authority: US
Inventors: Larry Keith Clark; Frank Willis Hill
Original assignee: Gulf and Western Industries Inc
Current assignee: Gulf and Western Industries Inc
Priority date: 1966-10-12
Filing date: 1966-10-12
Publication date: 1970-08-04
Anticipated expiration: 1987-08-04

Description

Aug. 4, 1970 L. K. CLARK ET L 3,

TIMED DECISION LOAD CONTROL S YSTEM FIG. 2

LAo

AND

BY Mm, 7M 8 Body RESET DISABLE l t e m A w s 2 a D e h s H 5 r C L :11 Firm WNW IA L m.

Filed Oct. 12, 1966 FIG I ADD DISABLEJVM RESET EXTER NAL SECON DARY STARTER TIME STARTER Aug.

Filed Oct. 12. 1966 AC. T0 0.0 L4 CONVERTER AND A.C.TO D.C. isss-zsn} (A.C.) CONVERTER EPE% 88 NV R AND /86 sse-v Q Dl, D2

Lu K- TIMED DECISION LOAD CONTROL SYSTEM CLARK ET 5 Sheets-Sheet 2 Kim-3 RECALL CRI OFF

MEMORY I L| i (IRE-3 l "he E 1NVENTOR5. '2 P LARRY K. CLARK 81 $W'3 FRANK W. HILL FIG. 3

Maya, 114m; 61 8nd;

ATTORN EYS L L. K. CLARK ET AL TIMED DECISION LOAD CONTROL Aug. 4, 1970 SYSTEM 5 Shets-Sheet 5 Filed Oct. 12, 1966 7 76 ADD A.C.TO D.C. CONVERTER J COMPARATOR I PASSAGE TIME TlMER "3;""" """1 I +Vl V0 I I Ei 1 ?E I d TIME WAITING-MINIMUM LuLL INVENTORS- LARRY K. CLARK a FRANK; w. HILL Amo 0.0. CONVtHItH :W 8+ I02 ||O-\ RAND 6 M \I04 TIMER FIG. 3A

ATTORNEYS Aug. 4, 1970 L. K. CLARK T TIMED DECISION LOAD CONTROL SYSTEM 5 Sheets-Sheet 4 Filed Oct. 12. 1966 Ll (ExcEPT DURING STEP POSITIONS 3 AND) ,8)

COMPARATOR +vt 0 f 34 I Q EXTENSION LIMIT AN 0 GREEN No. 2 TIMER SW-G F ROM CR2-3 .1 w Q I I r w R S AAIYNHS B 8 L 6 S E I W I E I R S I I ll B B B C W Q W O M I. m m m m m 0/0 8 %F F O 6 m w wm E I s s W P w A5 1 B ob i \2 H 8 N B W R C O. S C ,R w w m m 5 A m l? w 0 R M 2 C CO R 0 E INVENTORS. LARRY K. CLARK 8a FRANK W. HILL Mew, 7M 8 ulf FIG. 3B

ATTORNEYS Aug. 4, 1970 K. CLARK ET TIMED DECISION LOAD CONTROL SYSTEM 5 Sheets-Sheet 5 Filed Oct. 12. 1966 m m m v W W OE owm \wmmz zmmmw r Sm 29KB $232 33 M21. M3025 k 1 EFF Kwwmvw zwwmw cum hmumkm mwomo LARRY K. CLARK 8a BY FRANK w. HILL Mm,7d6mq 880d;

ATTORNEYS 3,522,581 Patented Aug. 4, 1970 US. Cl. 340-37 15 Claims ABSTRACT OF THE DISCLOSURE A load control system is disclosed herein which is particularly applicable to traffic controllers. Specifically, a trafiic controller is disclosed which incorporates a minimum initial timer, a variable initial timer, and a unit extension timer. Circuitry is provided for concurrently energizing the three timers so that they all commence their timing functions at substantially the same point in time. In this manner, and especially during light traffic conditions, the unit extension timer may have at least partially completed its timing function prior to the point in time that the minimum initial and variable initial timers have completed their timing functions.

DISCLOSURE This invention relates to the art of timing and more particularly, to a plurality of timers which may time concurrently to control energization of a load.

The invention is particularly applicable in conjunction with trafiic control and will be described with particular reference thereto; although, it is to be appreciated that the invention may be used, for example, in conjunction with timed control of conveyor systems or timed control of industrial processes.

A trafiic actuated controller serves to control the operation of a traffic intersection signal displaying go, caution and stop signals to two or more intersecting traflic phases in accordance with traffic demand as registered with the controller by vehicle detectors in the traffic actuated phases. Traffic actuated controllers, either semiactuated or full actuated, known heretofore have included, for each traflic actuated phase, a minimum initial timer, a variable initial timer, a vehicle extension timer, and an extension limit timer.

A minimum initial timer serves to time a predetermined minimum period of go time to permit a given number of vehicles in the actuated tratiic phase to commence movement through the intersection. A variable initial timer serves to time an adjustable period of go time dependent on the number of vehicles detected in the actuated phase during the previous period of time that a stop signal was displayed to that phase. A resettable vehicle extension timer serves to time at least one additional-increment of go time, known as a vehicle extension period, with the vehicle extension period being sufficient to permit the vehicle to travel from the detector in the actuated phase to the stop line. The vehicle extension timer is reset by each vehicle detected in the actuated phase once a go signal has been displayed to that phase. An extension limit timer, sometimes referred to as a maximum timer, serves to time a maximum allowable period of go time for the actuated phase. Normally, the minimum initial and variable initial timers are initially energized at the same time so that they may commence their timing functions concurrently, with the last to time out serving to provide a control signal for initiating termination of an initial go interval for the actuated phase. The unit extension timer is then energized to time at least one additional increment of go time for the actuated phase.

A notatable problem with such traffic controllers, as described above, occurs during light traffic conditions. More particularly, when traflic volume is light both the minimum initial and variable initial timers must time out before the unit extension timer can commence its timing function. Accordingly, under such. light trafiic conditions there may be no need to provide an additional increment of go time during the vehicle extension period and, hence the allocation of such go time constitutes an unnecessary waste of go time being allocated to the associated traffic actuated phase.

The present invention is directed toward circuitry particularly applicable for use with traffic controllers so that the minimum initial, variable initial, and unit extension timers concurrently time their respective timed intervals, whereby during light traffic conditions the unit extension timer may have at least partially completed its timing function prior to the point in time that the minimum initial and variable initial timers have completed their timing functions, thereby overcoming the noted disadvantages and others of previous traflic controllers.

In accordance with one aspect of the present invention, it is contemplated that a controller serves to control stop and go movement of movable means, such as Vehicles, through an intersection of at least two flow paths, such as trafiic phases, of movement of the movable means and wherein at least one of the paths has detection means associated therewith for detecting each said movable means in the associated path.

More particularly, the controller includes for each flow path: first timing means, such as minimum initial timing means for timing a predetermined .minimum go signal initial interval, and then developing a first signal; second timing means, such as variable initial timing means controlled by the associated detection means for timing a variable go signal initial interval in accordance with the number of vehicles detected by the detection means during the preceding period of time that a stop signal is displaced to an actuated phase, and then developing a second signal; third timing means, such as vehicle extension timing means for timing at least a predetermined vehicle extension period of time, and then developing a third signal; starting means for initially and concurrently energizing the first, second and third timing means so that all of these timing means commence their timing functions at substantially the same point in time; AND circuit means for developing an initial interval termination signal only when both the first and second signals have been developed; second AND circuit means responsive to the initial interval termination signal and the third signal for developing an extension interval termination signal only when both the initial termination signal and the third signal have been developed; and, interval control means responsive to the interval termination signals for terminating the initial go interval in response to the initial interval termination signal and terminating the vehicle extension interval in response to the extension interval termination signal.

In accordance with a still further aspect of the present invention, the traflic controller includes reset means controlled by the associated detection means for resetting the vehicle extension timing means in response to each detection of a vehicle in the actuated phase so that the vehicle extension timing means commences to time another vehicle extension period.

In accordance with a still further aspect of the present invention, the controller includes extension limit timing means for timing a predetermined time limit for the go signal displayed to the actuated phase, and then developing a fourth signal; and, reset disabling means responsive to the fourth signal for disabling the reset means, whereby the vehicle extension timer means completes its timing function, and then develops the third signal.

The primary object of the present invention is to provide improved circuitry for energizing several timers so that they time together concurrently for energizing a load.

A still further object of the present invention is to provide timing circuitry which is relatively simple in manufacture and economical in operation.

A still further object of the present invention is to provide an improved traffic controller wherein various timing periods timed by the controller are timed concurrently.

A still further object of the present invention is to provide an improved traffic controller for minimizing wasted right-of-way time during an operation cycle.

A still further object of the present invention is to provide an improved trafiic controller wherein the vehicle extension timer may time concurrently with the variable initial and minimum initial timers.

The foregoing and other objects and advantages of the invention will become apparent from the following description of the preferred embodiment of the invention as read in connection with the accompanying drawings in which:

FIG. 1 is a schematic illustration of a typical intersection to which the present invention may be applied;

FIG. 2 is a block diagram of the preferred embodiment of the invention;

FIGS. 3, 3A and 3B, taken together, is a single figure of a block diagram of a traific controller incorporating the preferred embodiment of the invention illustrated in FIG. 2; and,

FIG. 4 is a chart illustrating trafiic intervals corresponding with step switch positions.

Referring now to the drawings, and more particularly to FIG. 2, there is shown a preferred embodiment of the invention for controlling the operation of load L, such as a step switch driver coil in a traffic controller, wherein the circuit generally comprises a starter C, timers T1, T2, T3, T4 and a secondary starter E. Timers T1, T2, T3 and T4 may take various forms, such as electromechanical timers or electronic timers, such as RC unijunction relaxation oscillator circuits.

As shown in FIG. 2, timer T1 has its input circuit connected to starter C, and its output circuit connected to an AND circuit 12. Timer T2, which times in parallel with timer T1, has its input circuit connected to starter C, and its output circuit connected to the input circuit of AND circuit 12. The input circuit of timer T2 is also connected to starter C through a time add disable circuit 14 and a time add circuit 16. Time add disable circuit 14 is connected with an external reset circuit 18, which in turn is connected to the input circuit of timer T3 through a reset disable circuit 20. The input circuit of timer T3 is also connected to starter C and the output circuit of the timer is connected to the input circuit of an AND circuit 22. AND circuit 12 has its output circuit connected to the circuit of an OR circuit 24, as well as to an input circuit of AND circuit 22, which in turn has its output circuit connected to the input circuit of OR circuit 24. Timer T4 has its input circuit connected through an AND circuit 26 to starter C and secondary starter E, and its output circuit connected to the reset disable circuit 20. The secondary starter E also has its output circuit connected to an input circuit of AND circuit 22.

OPERATION Starter C applies a start signal to energize timers T1, T2, and T3. Each of these timers times its time delay period and then develops an output signal, such as a positive potential. Timer T1 times a predetermined minimum initial period of time before developing an output signal.

In traflic control applications this timer may be a normal timer for timing a vehicle minimum initial interval. Timer T2 serves to time a variable period of time in accordance with the number of output pulses from the external reset circuit 18. Thus, for each external reset pulse, one increment of time is added to timer T2 through the time add disable circuit 14 and the time add circuit 16. The total period of time timed by timer T2 may be less than or greater than the fixed period of time which is timed by timer T1. When both timers T1 and T2 have completed their timing functions, an output signal is developed by AND circuit 12. This output signal, Which may be considered as a binary (1) signal, is applied through OR circuit 24 to energize load L. Similarly, this output signal is also applied as one of the inputs to AND circuit 22.

Timer T3 serves to time at least one fixed interval of time and then develop a third output signal. This timer may serve as a resettable vehicle extension timer for traffic applications. The timer is reset by each output pulse from external reset circuit 18 through the reset disable circuit 20. For traffic purposes, the external reset circuit may take the form of a vehicle detector circuit. When timer T3 times out, it develops an output signal for application to the input circuit of AND circuit 22. However, an output signal is not present on the output circuit of AND circuit 22 until an input signal is applied to the third input circuit of the AND circuit itself.

Timer T4 commences its timing function only when supplied with start signals from starters C and E. A start signal from starter B provides the third input signal for AND circuit 22. In the event, however, that timer T3 has not completed its timing function, such as due to it being constantly reset by external reset pulses, timer T4 times a predetermined fixed period of time and develops an output signal for disabling the reset disable circuit 20. For traific applications, timer T4 may take the form of an extension limit timer. When the reset disable circuit 20 is disabled, timer T3 can no longer be reset and, hence, it completes its timing function and develops an output signal for application to AND circuit 22. Since all three inputs are now applied to the AND circuit 22, an output signal is developed on its output circuit for application through OR circuit 24 to energize load L.

Having now generally described the preferred embodiment of the invention, attention is directed to the following detailed description of the invention as applied to a traflic controller.

TRAFFIC CONTROLLER Referring now to FIGS. 1, 3 and 4 wherein the showings are for purposes of illustrating a preferred embodiment of the invention only, and not for limiting same, there is illustrated in FIG. 1 a typical intersection of two trafiic phases, phase A and phase B. Adjacent the intersection of the two phases there is schematically illustrated stop lines SL which may be located as desired by municipal traffic engineers. At each aproach to the intersection there is provided a detector, i.e., detectors D1 and D2 for the app-roaches of phase A, and detectors D3 and D4 for the approaches of phase B. Detectors D1, D2, D3 and D4 preferably take the form of loop detectors, which are well known in the art of traflic control, and generally comprise a closed wire loop embedded in a roadway, with the loop configuration defining an area under surveilance by the detector, which together with associated circuitry develops an output signal so long as a vehicle is present within the area under surveilance. Alternatively, detectors D1, D2, D3 and D4 may take the form of other detectors, such as overhead mounted untrasonic detectors which, in a manner similar to that of loop detectors, serve to monitor or survey a predetermined area on the roadbed for the presence of vehicles and provide an output signal as long as a vehicle is present in the area under surveilance. Further, the detectors may also take the form of spot detectors, such as the familiar tread pad, which together with its associated circuitry provides an output signal in response to each actuation by a vehicle momentarily passing over the spot detector. In the event that the detectors take the form of loop detectors, as shown in FIG. 1, it is preferably that each detector, as illustrated with respect to detector D3 in FIG. 1, have a width w which is sufficiently wide to detect vehicles in all of the lanes in the approach to the intersection; a length l which extends in the direction of the phase for a distance less than the length of one vehicle, such as, for example, on the order of four feet; and, be located at a distance a from the stop line, which distance may be on the order of twohundred feet. The detectors D1, D2, D3 and D4 are connected to a local controller LC, which controls the operation of an intersection trafiic signal S which displays go, caution and stop signals to phases A and B. Preferably, in accordance with the present invention, loop detectors D1 and D2 are connected to a phase control unitA for controlling the signal displays by traflic signal S to phase A and detectors D3 and D4 are connected to phase control unit B for controlling the signal displays by trafiic signal S to phase B.

The traffic controller to be described hereinafter takes the form of a two phase, full actuated, trafiic controller including a phase control unit for each traffic phase. The invention is not limited to such a traflic controller but may be used with other controllers, such as, for example, a semiactuated, two phase, trafiic controller or a two or more phase, full actuated, trafiic controller wherein all of the control circuitry is included within a given unit as opposed to phase control units described with reference to FIG. 3.

As shown in FIG. 1, local controller LC includes two phase control units A and B for respectively controlling phase A and phase B trafi'ic flow. Phase control units A and B are substantially identical and, accordingly, only phase unit A is described hereinafter in detail, it being understood that the description applies equally to phase unit B.

Referring now to FIG. 3, phase unit A generally cornprises five timers; namely, a normal timer T1, a variable initial timer T2, a passage time timer T3, an extension and green No. 2 timer T4, and a time waiting-minimum lull timer T5; and, an eight bank, eleven position step switch SS for controlling the operation of the phase A signal lights of trafiic signal S through load relays LR in response to actuation of the phase A vehicle detectors D1, D2.

As will become evident from the description that follows, phase control unit A includes various TIMER cir-, cuits, NOR circuits, AND circuits, OR circuits, and AND (A.C.) circuits. To facilitate the understanding of this invention, each of these circuits is briefly explained below.

TIMER CIRCUIT.This is a static, solid state means timing circuit having an input circuit and an output circuit. Upon application of the ground potential signal, known as a (0) signal, the timer commences its timing function and upon completion thereof develops at its output circuit a positive potential signal, known as a (1) signal.

NOR CIRCUIT.-This is a static, solid state means circuit having one or more input circuits and one output circuit. A (0) signal is present at its output circuit whenever a (1) signal is applied to any of its input circuits. If a (0) signal is present on all of its input circuits, a (1) signal is present on its output circuit.

AND CIRCUIT.This is a direct current static, solid state means circuit having two or more input circuits and one input circuit. A (1) signal is present at its output circuit so long as all of its input circuits receive a (1) signal. If a (0) signal is present at any of its input circuits, a (0) signal is present at its output circuit.

OR CIRCUIT.This is a static, solid state means circuit having two or more input circuits and one output circuit. A 1) signal is present at its output circuit so long as any of its input circuits receive a (1) signal.

AND (A.C.) CIRCUIT.-This is a static, solid state means circuit, such as a transformer, having two input circuits and an output circuit which serves to develop an alternating current output signal at its output circuit only when one of its inputs is connected to ground potential and the other of its inputs is connected to the hot side of an alternating current voltage source.

STEP SWITCH Step switch SS preferably takes the form of an eight bank, eleven position step switch. If desired, the step switch may take the form of an electronic ring counter having the capability of cyclically stepping through eleven positions. As is well known to those skilled in the art, step switch SS cyclically steps through eleven positions, during which various circuits are completed by means of load relays LR for energizing the traflic signal lights S. Various load relay combinations may be made in accordance with a trafiic engineers schedule. From FIG. 4 it will be noted that step position Nos. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 are respectively the special clearance No. 2, minimum and density initial, green dwell, passage time and time waitingminimum lull, vehicle clearance No. 1, special clearance No. 1, green No. 2, green, dwell, vehicle clearance N0. 2, red dwell No. 1, and red dwell No. .2 intervals. As will be noted in the description which follows, the phase unit illustrated in FIG. 3 may be a single phase unit (option 2) for controlling a single trafiic actuated phase, or may be used as a semiactuated, two phase traffic controller (option 1) for controlling main street in accordance with a pretimed schedule and cross street traffic flow in accordance with traffic demand. The phase controller may be converted to a semiactuated traflic controller by opening normally closed switches SW-l, SW-2, SW-3, SW- t, SW-S and closing normally open switches SW-6, SW-7. For semiactuated operation (option 1, see FIG. 4),

step switch intervals

10, 11 and 1 through 6 may be the main street red (stop) period, intervals "7 and 8 may be the main street green (go) period, and interval 9 may be the main street amber (caution) period. Also, step switch positions 6 through 11 and 1 may he the cross street red period, positions 2 through 4 may be the cross street green period, and position 5 may be the cross street amber period. With switches SW-l through SW-7 in a position as shown in FIG. 3, the circuit serves as a single phase, fully actuated, phase control unit (option 2, see FIG. 4) during which step positions 10, 11 and I serve as the actuated phase red (stop) period, step positions 2 through 8 serve as the actuated phase green (go) period, and step position 9 serves as the actuated phase amber (caution) period.

NORMAL TIMER Normal timer T1, like timers T2, T3, T4 and T5, generally comprises a linear ramp function generator 30 and a differential amplifier circuit serving as a comparator circuit 32. Generator 30 includes a DC. amplifier 34 and a negative feedback capacitor 36. Briefly, upon application of a (0) signal to the input circuit of generator 30, an output voltage V appears at its output circuit, which potential linearly increases in value with elapsed time, as shown by the wave form adjacent generator 30 in FIG. 3. The comparator 32 serves to compare the value of the linearly increasing output voltage V with a reference voltage V and develop a positive direct current voltage output signal, known as (1) signal, when the value of the two potentials is substantially equal.

The reference voltage V applied to one of the input circuits of comparator 32 is obtained from one of five

potentiometers

38, 40, 42, 44 and 46. Each of the potentiometers has its resistance connected between ground and the B+ voltage supply source through contacts on step switch SS. Accordingly, it is appreciated that the time delay required for the output voltage V of generator 30 to reach 7 the value of the reference voltage V is dependent on the adjustment of the particular potentiometer in effect during the appropriate step position.

As discussed above, the

various potentiometers

38, 40, 42, 44 and 46 are connected through step switch contacts to the B+ voltage supply source. As is well known to those skilled in the art, each time that a step switch is energized, it steps one step to close one switch in each bank until the step switch is stepped to the next step posimally open switch contacts on the eight banks in step position. Thus, for example, in step switch position 6 all nortion 6 are closed. Reference is now made to potentiometer 38 which has its resistance portion connected between ground and the B+ voltage supply source through normally open step switch contacts located at bank 6, position I, referred to in the drawings as SS6-1. Similarly, potentiometer 40 is connected to the B+ voltage supply source through step switch contacts at bank 6, position 2, SS62. Similarly,

potentiometers

42, 44 and 46 are respectively connected to the B+ voltage supply source through step switch contacts SS6-5, 556-6 and 556-9. It will be noted that these step switches are closed at different positions of the step switch, no two being closed at the same time. Thus, potentiometer 38 serves to adjust the time duration of special clearance No. 2 interval. Potentiometer 40 serves to adjust the time duration of the minimum initial interval, potentiometer 42 serves to adjust the time duration of vehicle clearance No. l interval, potentiometer 44 serves to adjust the time duration of special clearance No. 1 interval, and potentiometer 46 serves to adjust the time duration of a special clearance No. 2 interval. These step switch positions and traffic intervals are illustrated in the chart of FIG. 4.

The input circuit of ramp function generator 30 is connected through a potential divider 48 to the B+ voltage supply source, as well as through a normally open interrupter contact S.S.INT.A to the 13+ voltage supply source. Interrupter contacts A are located on the step switch and momentarily close each time that the step switch is stepped from one position to the next. Thus, each time the step switch is actuated a 1) signal, i.e., B+ voltage, is applied to the input circuit of generator 30 to reset the generator so that its output voltage V is referenced to ground prior to commencing a timing operation.

The input circuit of the normal timer T1, taken at the input of generator 30, is connected to the output circuit of a NOR circuit 50, which, in turn, has its input circuit connected to a source of alternating current voltage L4 through an AC. to DC. converter 52. The alternating voltage source L4 is preferably the hot side of an alternating current voltage source, which has its other side connected directly to ground. The ground side of the alternating current voltage source will hereinafter be referred to either as ground or the L1 voltage supply source. The converter 52 serves to convert the alternating current voltage into a positive potential known as a (1) signal for application to NOR circuit 50 so that so long as there is no disruption in the voltage source L4, a (1) signal is applied to the input circuit of NOR circuit 50, whereupon a (0) signal is applied from the output circuit of NOR circuit 50 to the input circuit of timer T1. The output circuit of timer T1, as taken at the output circuit of comparator circuit 32, is connected to the input circuit of an OR circuit 54, having its output circuit connected to the input circuit of an AND circuit 56. The output circuit of AND circuit 56 is connected to an input circuit of an OR circuit 58 having its output circuit connected to the input circuit of another AND circuit 60. The output circuit of AND circuit 60 is connected to ground through relay coil CR4-C of a control relay CR4.

VARIABLE INITIAL TIMER The variable initial timer T2 is substantially identical to normal timer T l and, accordingly, like components are identified in FIG. 3 with like reference characters. The

variable voltage V for comparator circuit 32 of timer T2 is taken from a voltage divider 62 connected between ground and the B+ voltage supply source. The output circuit of the timer, as taken from the comparator circuit 32, is connected to an input circuit of AND circuit 56. The input circuit of timer T2 is connected to a B+ voltage supply source through a START circuit 64 and normally open step switch contacts SS6-Z at step switch bank 6, position 2. The input circuit of timer T2 is also connected to the output circuit of a NOR circuit 66, which in turn has its input circuit connected to the output circuit of AC. to D.C. converter 52. The variable initial timer serves to time a variable period of time in accordance with the number of actuations of phase A vehicle detectors D1, D2 and this function is provided by means of a time add circuit 68 connected to the input circuit of amplifier 34. The time add circuit is adjusted by a potentiometer 6 and has its input circuit connected to the B+ voltage supply source through normally open relay contacts CR1-2 of relay CR1, and step switch normally open contacts 856-1, 10, 11 so that whenever contacts CRl-Z are closed, during

step positions

1, 10 and 11, B+ potential is applied to the time add circuit. Preferably, the variable initial timer is set so that it provides a time increment between one and five seconds for each vehicle actuation.

PASSAGE TIME TIMER The passage time timer T3 is substantially identical to the normal timer T1 and, accordingly, like components are identified by like reference numerals in FIG. 3. The passage time timer serves upon actuation to time a passage time, otherwise known as a unit extension time, which is the time required for a vehicle to traverse the distance from the phase A vehicle detectors D1, D2 to the stop line SL at the intersection (see FIG. 1). This time is normally set in the range from 0 to 30 seconds, according to a traflic engineers schedule. The reference voltage V for comparator circuit 32 of timer T3 is obtained from an adjustable passage time potentiometer 68. The output circuit of the timer is taken from the output circuit of comparator 32 and is connected to the input circuit of an AND circuit 70, having a second input taken from the B-lvoltage supply source through normally open step switch contacts SS6-4. The output circuit of AND circuit 7% is connected to the input circuit of OR circuit 54.

The input circuit of timer T3, as taken at the input circuit of the ramp function generator 30, is connected to the output circuit of an OR circuit 72. The input circuit of OR circuit 72 includes one input connected to the output circuit of NOR circuit 74, which in turn has its input circuit connected to the output circuit of the AC. to DC. converter 52. A second input circuit of OR circuit 72 is connected to the output circuit of a NOR circuit 76, which in turn has its input circuit connected through an AC. to DC. converter 78 to the L4 voltage supply source by means of normally open step switch contacts SS12, 3, 4. A third input circuit of OR circuit 9. A system for monitoring and adjusting power de- CR1-3 of relay CR1, to the B+ voltage supply source, through normally closed relay contacts CR32 of relay CR3.

EXTENSION LIMIT AND GREEN NO. 2 TIMER The extension limit and green No. 2 timer T4 is substantially identical to the normal timer T1 and, accordingly, like components are identified with like reference characters in FIG. 3. The reference voltage V for the comparator circuit 3.2 of timer T4 is obtained in

step positions

2, 3 and 4 from the B+ voltage supply source through potentiometer 80 and normally open step switch contacts 586-2, 3, 4. In step position 7, the reference voltage V is obtained from the 13+ voltage supply source through potentiometer 82 and normally open step switch contacts SS67. Potentiometer 8% serves to adjust the maximum duration of the extension limit period and potentiometer 82 serves to adjust the time duration of the green No. 2 interval (see FIG. 4).

The input circuit of timer T4, as taken at the input circuit of linear ramp function generator 3 0, is connected to the output circuit of a NOLR circuit 84, having its input circuit connected to the output circuit of an AND circuit 86. One input circuit to AND circuit 86 is connected to the B+ voltage supply source through normally open step switch contacts SS6 -7. The other input circuit for AND circuit 86 is connected through an A.C. to D-.C. converter 88 to the alternating current voltage supply source L4.

The input circuit of timer T4 is also connected to the output circuit of a NO R circuit 90, having its input circuit connected to the output circuit of an AC. to DC. converter 92. The input circuit of the converter 92 is in turn connected to the output circuit of an AND (A.C.) circuit 94. AND circuit 94 may take the form of a transformer having its secondary winding connected to converter circuit 92 and its primary winding serving as an input circuit, with one end of the primary winding being connected to the alternating current voltage source L4 and the other end of the primary Winding being connected to ground through step switch contacts SSS2, 3, 4, a normally closed switch SW-3 and, in phase unit B through normally open relay contacts CR2-3 (which correspond with the like numbered contacts in phase unit A), and thence through the phase B step switch contacts SS7-10, 11. This portion of the circuitry of phase unit B is shown in FIG. 3 only for purposes of clarifying the manner of interconnection of phase units A and B.

The output circuit of timer T4, taken at the output circuit of comparator 32, is connected to one input circuit of an AND circuit 96, having another input circuit connected to the B+ voltage supply source through normally open switch contacts 586-7. The output circuit of AND circuit 96 is connected to an input circuit of OR circuit 58. The output circuit of timer T4 is also connected to the input circuit of another AND circuit 98, having a second input circuit connected to the B+ voltage supply source through normally open step switch contacts 586-2, 3, 4; The output circuit of AND circuit 98 is connected to one input circuit of an OR circuit 100. The output circuit of OR circuit 100 is connected to ground through relay coil CR3-C of relay CR3.

TIME WAITING-MINIMUM LULL TIMER The time waiting-minimum lull timer T5 is substantially identical to the normal timer T1 and, accordingly, like components in both circuits are identified with like reference characters in FIG. 3. A major distinction, however, between timer T5 and the normal timer T1 is that the generator 30' of timer T5 is the complement of generator 30 in timer T1. That is, as will be noted from a comparison of the wave forms associated with the circuitry of timer T1 or T5, the value of output voltage V of timer T1 linearly increases in a positive direction with elapsed time, whereas the value of output voltage V of timer T linearly decreases toward ground potential with elapsed time. The reference voltage V for comparator circuit 32 of timer T5 is taken from the output circuit of generator 30 in timer T3 so that the reference voltage V is equal to the value of output voltage V of generator 30 in timer T3. Accordingly, timer T5 serves to compare the linearly decreasing voltage V from generator 30 with the linearly increasing reference voltage V taken from the generator 30 of timer T3.

The input circuit of timer T5, as taken at the input circuit of generator 30, is connected through a time waiting adjustable potentiometer 102 to the junction of a potential divider 104. The potential divider 104 is connected between the wiper arm of potentiometer 68 of timer T3, and the wiper arm of a minimum lull adjustable potentiometer !106, which in turn is connected between ground and the B+ voltage supply source.

The input circuit of timer T5 is also connected to the output circuit of a NOR circuit 108, having its input circuit connected to the output circuit of an AC. to DC. converter 112. Converter '112 is connected to the output circuit of an AND (A.C.) circuit 110. One of the input circuits of AND (A.C.) circuit 110 is connected to power source L4 and the other of its input circuits is connected through normally open step switch contacts SS84, normally closed switch SW-3, and in the phase B control unit through normally open relay contacts CR2-3 and, thence, through step switch contacts SS7-10, 11 to ground.

RELAY CIRCUITS To some extent, the description given hereinabove with respect to the timers T1, T2, T3, T4 and T5 has included description as to the circuit interconnection with relays CR1, CR2 and CR3. Relay CR1 may be termed as the vehicle detection relay and includes relay coil CR1-C which is connected between a 12 volt alternating current voltage source, labeled as 12 V. AG. in FIG. 3, and ground through phase A detectors D1, D2 which are illustrated in the circuit as a normally open switch. Relay CR1 includes normally open relay contacts CR1-1, CR1-2 and CR1-3. These contacts have been discussed hereinbefore with respect to their interconnection with the timer circuits. In addition to the interconnections previously described with respect to the timer, it will be noted from FIG. 3 that contacts CR1-1 are connected to ground through relay coil CR2-C of memory relay CR2. Relay CR2 also includes normally open relay contacts CR2-2 and CR2-3. Relay CR3, which includes relay coil CR3-C connected between the output circuit of OR circuit and ground, also includes normally open relay contacts CR3-1 and normally closed relay contacts CR3-2. In addition, the relay circuits also interconnect with a recall switch SW-10, which includes a pair of ganged

movable contacts

116 and 118.

Movable contacts

116 and 118 are four position contacts, and may be positioned in either one of four positions; namely, maximum, recall, olf, and eX- ternal memory. In the off position, contact 116 serves together with relay contacts CR2-2 to provide a shunt circuit across normally open detector relay contacts CR1-1. Thus, whenever relay coil CR1-C is energized, to energize relay coil CR2-C (when in

step positions

1 and 5 through 11), relay contacts CR2-2 close to provide a shunt path across contacts CR1-1 to maintain relay coil CR2-C energized. With switch SW-10 in its recall position, movable contact 116 connects relay coil CR2-C between ground and the alternating current voltage source L4 (in

step positions

1 and 5 through 11) to maintain the memory coil in a constant recall condition. When switch SW-10 is in its maximum position, movable contact 118 connects detector relay coil CR1-C between ground and the 12 volt alternating current voltage source so as to constantly energize the detector relay coil. When switch SW-10 is in its external memory position, the memory function is performed by external memory means such as a presence detector which, as described hereinbefore, provides an output signal so long as a vehicle is present within its zone of influence. In addition to the foregoing, it will be noted that relay contacts CR3-1 serve, when closed, to provide a shunt between voltage source L4 and relay contacts CR1-1. Also, memory relay contacts CR2-3 serve, when closed during step positions 10 and 11, to provide a vehicle calling signal, representative that a vehicle on phase A demands right-of-way movement through the intersection, to the phase B phase control unit through normally closed switch SW-3.

STEP SWITCH DRIVER CIRCUIT The step switch driver circuit includes relay coil CR4-C, of relay CR4, in the output circuit of AND circuit 60. Relay CR4 includes a set of normally open contacts CR4-1 which serve to connect a step switch driver coil CRS-C between the alternating current voltage source L4 and ground through diode 120. The step switch SS is driven one step, in a manner well known in the art, in response to each energization of driver coil CRC. The step switch is driven from step position 3 to step position 4 when a circuit is completed across coil CRS-C from the alternating current voltage source L4 through normally closed interrupter contacts CR5INT-C, off normal contact 122, normally open step switch contacts SSS-3, normally closed switch SW3, normally open relay contacts CR23 (in phase unit B) and normally open phase B step switch contacts SS710, 11 to ground. The off normal contacts 122 are controlled by the step switch and are normally open, except in step position 3. The normally closed interrupter contacts CRS-INT-C are controlled by driver coil CRS-C and are open during the period that the coil is energized.

The input circuit of AND circuit 60 is connected to the output circuit of a NOR circuit 124. One of the input circuits of NOR circuit 124 is connected to a source of L1 power (ground) except during

step positions

3 and 8.

The step switch SS is stepped from its step position 3 to its step position 4 by the circuit described above with respect to the off normal contacts 122 and the interrupter contacts CR5INTC. The following description is given with respect to the circuit that is used for stepping the step switch SS from step position 8 to step position 9. This circuit includes a path taken from an input circuit of another NOR circuit 125, having its output connected to relay coil CR4C, through normally closed switch SW-5, normally open step switch contacts SSS-8 and, thence, through normally closed switch SW3 and into the phase B control unit through normally open relay contacts CR23 and step switch contacts 557-10, 11 to the L1 power source, i.e., ground. Accordingly, it is seen that the step switch cannot be stepped out of its

step positions

3 or 8 unless relay contacts CR2-3 in the phase B control unit are closed, representative of a vehicle demanding right-of-way movement on phase B. A second input circuit for NOR circuit 124 is taken through normally open switch SW6 (which is closed only for semiactuated operation) and thence to the junction between normally closed switch SW-4 and relay contacts CR23.

In local controller LC, which includes phase units A and B for controlling phase A and phase B trafiic flow, the phase unit associated with the traffic phase to which a stop signal is displayed normally dwells in red dwell No. 1 interval, at step position (see FIG. 4). When the phase unit associated with the phase to which a go signal is displayed is stepped from step position 8 to step position 9, it is desirable that the other phase unit be stepped from step position 10 to step position 11. Similarly, when the phase unit in control is stepped from step position 9 to step position 10, the other phase unit is stepped from red dwell No. 2 interval, at step position 11, to step position 1. The circuit for accomplishing this function is described below. Normally closed switch SW-l is connected from the junction of coil CRS-C and relay contacts CR41 to normally open phase A step switch contacts SS4-8, and thence to phase B step switch contacts SS410. Similarly, switch SW-l is connected through phase A step switch contacts SS4-9, 11, and thence to phase B step switch contacts SS4-9, 11. Switch SW-Z serves to connect the junction of switch SW1 and coil CRS-C through phase A step switch contacts SS4-10 to the phase B step switch contacts SS4-8. Also, switch SW-2 is connected through phase A step switch contacts 854-9, 11 to phase B step switch contacts 854-9, 11. The operation of these circuits will be appreciated from the detailed description which follows.

OPERATION Phase A, step position 10 A cycle of operation for phase unit A of local controller LC commences, for example, when phase unit A is in its red dwell No. l interval, i.e., step position 10.

When phase B is stepped from its step position 8 to its step position 9, L1 power is applied from phase unit B through now closed step switch contacts 534-8, through now closed phase A step switch contacts 584-10, and thence through switch SW-2 to complete an energizing circuit for phase A step switch coil CRS-C. Accordingly, this steps the step switch SS in phase unit A from step position 10 to step position 11, the phase A red dwell No. 2 interval. Simultaneously therewith, the phase B step switch is stepped from its step position 8 to its step position 9, as will be appreciated from the description which follows with reference to phase unit A.

Phase A, Step position 11 After phase unit B has timed its vehicle clearance No. 2 interval, i.e., step position 9, L1 power is applied from phase unit B through its now closed step switch contacts 554-9, through the now closed phase A step switch contacts 584-11, and thence through switch SW-2 to complete an energizing circuit for phase A step switch coil CRS-C. Thus, the phase A step switch SS is stepped from its step position 11 to step position 1, the phase A special clearance No. 2 (stop) interval. As will be appreciated from the description which follows, phase unit B is also stepped from its step position 9 to its step position 10, the red dwell No. 1 interval, where the phase B unit dwells until it becomes trafi'ic actuated. Phase unit A is now in control.

Phase A, Step position 1 In step position 1, phase A normal timer T1 times a fixed special clearance No. 2 interval, illustrated as a red or stop interval in FIG. 4. The time duration of this interval is determined by the value of the reference voltage V applied to comparator 32, as adjusted by potentiometer 38. As the step switch was stepped into step position 1, step switch interrupter contacts SS-INT-A momentarily closed to apply B+ potential, i.e., a (1) signal, to the input circuit of timer T1. This resets the timer so that as the switch reopens an energizing (0) signal is applied to the timer. In the event that the L4 power source fails, a (1) signal is applied from NOR circuit to the input circuit of timer T1, to constantly maintain the timer reset. In the absence of such power failure, however, timer T1 commences its timing function as the step switch steps to position 1. Accordingly, the output voltage V of generator 30 in timer T1 linearly increases until such time that the value of voltage V is substantially that of the reference voltage V whereupon a (1) signal is applied from the output circuit of comparator 32 to the input circuit of OR circuit 54. The OR circuit applies a (1) signal to the input circuit of AND circuit 56. The AND circuit 56, however, requires a second (1) input signal from the output circuit of comparator circuit 32 of timer T2 before it applies a 1) signal to OR circuit 58. As shown by the wave form associated with generator 30 of timer T2, the output voltage V is normally set so that it is above ground potential, i.e., close to B+ potential. Accordingly, in the absence of timer T2 being reset, an output signal, i.e., a (1) signal, is applied from the output circuit of comparator 32 of timer T2 to the AND circuit 56. AND circuit 56 applies a (1) signal through OR circuit 58 to the input circuit of AND circuit 60. AND circuit 60, in turn, receives a second (1) signal from the output cir cuit of NOR circuit 124, except during

step positions

3 and 8. Thus, a (1) signal is applied from the output circuit of AND circuit 60 to energize control relay coil CR4-C. This closes relay contacts CR4-1, completing an energizing circuit for step switch coil CRS-C. The step switch SS steps from its step position 1 to step position 2, the minimum and density initial interval.

13 Phase A, step position 2 As shown in FIG. 4, step position 2 is a go or green signal interval for phase A traific. At the commencement of this interval circuits are completed for energizing normal timer T1, the extension limit timer T4, the variable initial timer T2, the passage time timer T3, and relay coil CR3-C. The operation with respect to each these circuits is described below.

Upon advancement into the minimum initial interval, timer T1 is reset by step switch interrupter contacts SS- IN'T-A and the timer then commences its timing function. The reference voltage V is obtained from potentiometer 40 during step position 2 since normally open stepping switch contacts 856-2 are now closed. When the output voltage V of generator 30 is substantially equal to the reference V a (1) signal is applied through OR circuit 54 to the input circuit of AND circuit 56. AND circuit 56, however, does not apply a (1) signal to OR circuit 58 until a (1) signal is developed by the output circuit of variable initial timer T2. In step position 2, START circuit 64 associated with timer T2 is initiated to actuate timer T2 to commence its timing function. The minimum value of voltage V is adjusted by the time add circuit 68 so as to vary the time required for the output voltage V to be substantially equal to the reference voltage V The greater the minimum value of voltage V the lesser the time required to obtain an output (1) signal from timer T2 and, conversely, the lesser the minimum value of voltage V the greater the time required for timer T2 to develop an output (1) signal. The time add circuit 68 receives a B--|- signal during

step positions

1, 10 and 11 for each closure of vehicle de tector relay contacts CR12. Accordingly, the variable initial time is proportionally increased in accordance with the number of vehicles detected during the preceding period that a stop signal was displayed to phase A trafiic. The variable initial timer may be set by potentiometer 69 to provide approximately five seconds for each vehicle detection. When timer T2 completes its timing function, it applies a (1) signal to the input circuit of AND circuit 56, whereupon the AND circuit applies a (1) signal through OR circuit 58 to the input circuit of AND circuit 60. Since a (1) signal is applied to AND circuit 60 from the output circuit of NOR circuit 124, except during

step positions

3 and 8, a (1) signal is applied to energize control relay coil CR4-C, thereby completing an energizing circuit for step switch driver coil CR5C. Thus, the step switch SS is stepped from step position 2 to step position 3, the green dwell interval.

At the commencement of step position 2, a circuit is also completed for energizing the passage time timer T3. More particularly, in

step positions

2, 3 and 4 a circuit is completed from the alternating current voltage source v L4 through step switch contacts SS12, 3, 4, and thence through the AC. to DC. converter 78 for developing a (1) signal for application to NOR circuit 76. Accordingly, NOR circuit 76 applies a (0) signal through OR circuit 72 to the input circuit of timer T3. Also, so long as there is not a failure of L4 power, a (0) signal is applied by NOR circuit 74 through OR circuit 72 to the input circuit of timer T3. Thus, the passage time timer commences its timing function so as to time at least one passage time, as adjusted by potentiometer 68. The passage time timer may be reset by vehicle actuations in phase A, since for each actuation relay coil CRl-C is energized to close its contacts CR1-3. Closure of contacts CR1-3 applies a (1) signal from the B+ voltage supply source through normally closed relay contacts CR3-2 to OR circuit 72. This momentary application of a (1) signal through 0R circuit 72 resets timer T3 so that it commences to time a second passage time. When the passage time timer completes its timing function, a (1) signal is developed at its output circuit for application to AND circuit 70. However, a (1) signal is not applied from the output circuit of AND circuit 70 to the input circuit of OR circuit 54 in any step switch position other than step switch position 4. Accordingly, if passage time timer completes its timing function in interval 2 or .3, this will not actuate the step switch SS.

During light traffic conditions, the variable initial timer T2 may time out before the normal timer T1 completes its timing function. During heavy tramc conditions, however, the variable initial timer T2 may require considerable time to complete its timing function after the normal timer T1 has timed out. Thus, the phase A traflic would maintain right-of-way to the detriment of the phase B trafiic. The extension limit portion of timer T4 serves to time a maximum period of go time for phase A traflic, after a vehicle on phase B has registered its demand for right-of-way movement through the intersection. More particularly, any time during phase A step positions 2, 3 and 4 a circuit is completed for energizing time T4 when a vehicle actuation has occurred on phase B. Thus, when relay contacts CR2-3 in phase B become closed, representative of a vehicle actuation in phase B during phase B step position 10 or 11, L1 power is applied through the phase B step switch contacts SS7- 10, 11, the now closed relay contacts CR2-3 in phase B, and thence to the phase A unit through switch SW4, through phase A step switch contacts SSS-2, 3, 4, to AND (A.C.) circuit 94. So long as L4 power has not failed, AND (A.C.) circuit 94 applies an AC. signal to the AC. to DC. converter 92. Circuit 92, in turn, applies a (1) signal to the input circuit of NOR circuit 90, which, in turn, applies a (0) signal to the input signal circuit of timer T4 so that timer T4 may commence its timing function. The time duration of the extension limit period is determined by the adjusted value of the reference voltage V which during

step positions

2, 3 and 4 is obtained from potentiometer 80. When the extension limit portion of timer T4 completes its timing function, a (1) signal is applied from its output circuit to the AND circuit 98. During

step positions

2, 3 and 4, AND circuit 98 applies a (1) signal through OR circuit 100' to energize relay coil CR3-C of relay CR3. This, in turn, opens normally closed relay contacts CR3-2, thereby preventing further vehicle actuations on phase A from resetting the passage time timer T3. Accordingly, the passage time timer completes timing a passage time and then develops a (1) signal for application to AND circuit 70. If this occurs during

step position

2 or 3, then as soon as the step switch is stepped to step position 4, a 1) signal is applied by AND circuit 70 through OR circuit 54 to AND circuit 56.

Phase A, step position 3 When the step switch is stepped from step position 2 to step position 3, the phase A control unit is in its green dwell interval. This is not a timed interval. In order for the step switch to he stepped from step position 3 to step position 4, a vehicle actuation must occur in phase B. When a vehicle actuation has occurred in phase B, relay contacts CR2-3 in the phase B control unit are closed and L1 power is supplied through phase B step switch contacts 887-10, 11 through the now closed contacts CR2-3, and thence through switch SW-3 to phase A step switch contacts SS8-3, through the off normal con.- tacts 122, which are closed during step position 3, through the interrupter contacts CRS-INT-C to complete an energizing circuit for step switch driver coil CR5C. The step switch steps from step position 3 to step position 4. Accordingly, it is seen that if the phase B vehicle actuation took place during the phase A step position 2, the phase A green dwell interval would be substantially eliminated. Otherwise, the phase A control unit dwells in its green dwell interval until such time as a vehicle actuation occurs on phase B.

Phase A, step position 4 In step position 4, the phase A passage time and time waiting-minimum lull period, the step switch will be stepped to step position 5 as soon as the passage time timer completes its timing function so that AND circuit 70 provides a (1) signal through OR circuit 54 to AND circuit 56. As discussed hereinabove, the passage time timer will be forced to complete its timing function in the event that the extension limit portion of timer T4 completes its timing function. This occurs because when the extension limit timer completes its timing function, it develops an output signal which disables the reset feature of the passage time timer by energizing relay coil CR3-C, causing contacts CR32 to open. However, the time waitingminimum lull timer T5 also serves, during step position 4, to energize relay coil CR3C and thus disable the reset feature of the passage time timer. During step position 4, L1 potential is applied from phase unit B through phase B step switch contacts SS710, 11 and closed relay contacts CR2-3, representative of a phase B vehicle detection, and thence through switch SW3, and through phase A step switch contacts SS84 (A.C.) circuit 110. So long as L4 power has not failed, AND (A.C.) circuit 110 applies an alternating current voltage signal to converter circuit 112. Converter circuit 112 applies a signal to NOR circuit 108 which, in turn, applies a (1) signal to the input circuit of timer T5, causing the timer to commence its timing function. Since ramp function generator 30' is the complement of generator 30 of the normal timer T1, the output voltage V of generator 30' linearly decreases, as shown by the wave form associated with timer T5. The reference voltage V for comparator circuit 32 of timer T is the output voltage V of generator in the passage time timer T3. When the output voltage V of generator 30 is substantially equal to the reference V comparator 32 of timer T5 develops a (1) signal for application through OR circuit 100, energizing relay coil CR3-C. This opens relay contacts CR3-2, preventing further reset of passage time timer T3. Accordingly, the passage time timer T3 completes its timing of a passage time and applies a (1) signal to AND circuit 70. It is to be appreciated that it is possible for timer T 5 to time out after the extension limit portion of timer T4 and, accordingly, the extension limit time will control the point in time that the reset feature of the passage time timer is disabled. A (1) signal is applied through OR circuit 54 to AND circuit 56. Since the variable initial timer has previously timed out, a (1) signal is also applied from timer T2 to AND circuit 56, whereupon the AND circuit applies a (1) signal through OR circuit 58 to AND circuit 60. Since AND circuit 60 receives a (1) signal from NOR circuit 124, except during

step positions

3 and 8, a (1) signal is also applied from the output of AND circuit 60 to energize control relay coil CR4C. This closes relay contacts CR41 to complete an energizing circuit for step switch coil CRS-C. Accordingly, step switch SS steps from step position 4 to step position 5, the phase A vehicle clearance No. 1 interval.

Phase A, step position 5 The phase A vehicle clearance No. 1 interval is a go interval for phase A and is timed by normal timer T1. The time duration of this interval is dependent on the value of the reference voltage V applied to comparator 32 of timer T1, which voltage, in turn, is adjusted by potentiometer 42. When the output voltage V of generator 30 of timer T1 is substantially equal to the reference voltage V a (1) signal is applied from the output circuit of timer T1 through OR circuit 54 to the input circuit of AND circuit 56. Since a (1) signal is applied from the output circuit of the variable initial timer T2 to the AND circuit 56, a (1) signal is applied through OR circuit 58 to AND circuit 60. Since a (1) signal is also applied to the AND circuit 60 from the output cir cuit of NOR circuit 124, except during

step positions

3 and 8, a (1) signal is also applied from the output circuit of AND circuit 62 to energize relay coil CR4C. This closes relay contacts CR4-1 to complete an ener- 16 gizing circuit for step switch driver coil CRS-C. Thus, step switch SS steps from step position 5 to step position 6, the phase A special clearance No. 1 interval.

Phase A, step position 6 The phase A special clearance No. l interval is a go interval for phase A, as indicated in FIG. 4. This interval is timed by the normal timer T1. The duration of the interval is dependent on the value of the reference voltage V as adjusted by potentiometer 44. When the output voltage V of generator 30 is substantially equal to the reference voltage V the comparator circuit 32 of timer T1 applies a (1) signal through OR circuit 54 to the AND circuit 56. Since the variable initial timer T2 has completed its timing circuit, its comparator circuit 32 also applies a (1) signal to AND circuit 56. Accordingly, AND circuit 56 applies a (1) signal through OR circuit 58 to AND circuit 60. Since a (1) signal is also applied to AND circuit 60 from the output circuit of NOR circuit 124, except during

step positions

3 and 8, a (1) signal is applied from the output circuit of AND circuit 60 to energize control relay coil CR4C. This closes relay contacts CR4-1 which, in turn, completes an energizing circuit for step switch driver coil CRS-C. Thus, the step switch SS steps from step position 6 to step position 7, the phase A green No. 2 interval.

Phase A, step position 7 The green No. .2 interval is a go interval for phase A, as indicated in FIG. 4, and is timed by the green No. 2 portion of timer T4. The time duration of this interval is dependent on the value of reference voltage V which, during step position '7, is dependent on the adjustment of potentiometer 82. In step position No. 7, a B+ potential is applied through step switch contacts SS6-7 to the input circuit of AND circuit 86. In the absence of power failure of alternating current voltage source L4, a (1) signal is also applied to the AND circuit 86 from the AC. to DC. converter circuit 88. Thus, AND circuit 86 applies a (1) sginal to NOR circuit 84 which, in turn, applies a (0) signal to the input circuit of timer T4. Thus, timer T4 commences its timing function and, when the output voltage V of generator 30 is substantially equal to the reference voltage V a (1) signal is applied from the output circuit of comparator circuit 32 of timer T4 to the input circuit of AND circuit 96. A (1) signal is also applied to the input circuit of AND circuit 96 from the B+ voltage supply source through step switch contacts SS6-7. Accordingly, AND circuit 96 applies a (1) signal through OR circuit 58 to the AND circuit 60'. Since a (1) signal is also applied to the AND circuit 60 from the output circuit of NOR circuit 124, except during

step positions

3 and 8, AND circuit 60 applies a (1) signal to relay coil CR4C. This closes relay contacts CR4-1 for completing an energizing circuit for the step switch driver coil CRSC. Thus, the step switch SS steps from step position 7 to step position 8, the phase A green dwell interval.

Phase A, step position 8 The green dwell interval is not a timed interval. The phase A control unit will dwell in this position until such time as a vehicle actuation occurs on phase B. More particularly, it is possible that the trafllc actuation on phase B, which caused the phase A control unit to step from step position 3 has been lost, by the time the unit is advanced to step position 8, as by a malfunction in equipment operation. Accordingly, so that stop signals are not displayed to all phases during this condition, phase A control unit remains in step position 8. If the phase B traflic actuation is still in effect, or at such time that a phase B trafiic actuation occurs, a circuit is completed for energizing the step switch driver coil CRS-C. Driver coil CRS-C is energized by a circuit which commences in phase unit B from source Ll through phase B step switch contacts SS7-10, 11, through closed relay contacts CR2-3, representative of a phase B trafiic actuation, through switch SWG, and then through phase A step switch contacts SSS-8, switch SW-5 to NOR circuit 125. Thus, a (1) signal is applied from the output circuit of NOR circuit 125 to energize relay coil CR4-C. This closes relay contacts CR4-1 for completing an energizing circuit for the step switch driver coil CR5C. Thus, the step switch SS steps from step position 8 to step position 9, the phase A vehicle clearance No. 2 interval.

Phase A, step position 9 The vehicle clearance No. .2 interval is a caution interval for phase A, as indicated by the chart in FIG. 4-, and is timed by normal timer T1. The duration of this interval is dependent on the value of the reference voltage V as adjusted by potentiometer 46. When the output voltage V of generator 30 is substantially equal to the reference voltage V the comparator circuit 32 of timer T1 applies a (1) signal through OR circuit 54 to AND circuit 56. Since the variable initial timer T2 has completed its timing function, its comparator circuit 32 also applies a (1) signal to AND circuit 56. Accordingly, AND circuit 56 applies a (1) signal through OR circuit 58 to AND circuit 60. Since a (1) signal is also applied to AND circuit 60 from the output circuit for NOR circuit 124, except in

step positions

3 and 8, a (1) signal is applied from the output circuit of AND circuit 60 to energize control relay coil CR4-C. This closes relay contacts CR4-1, which, in turn, completes an energizing circuit for step switch driver coil CRS-C. Thus, the step switch S5 steps from step position 9 to step position 10, the phase A red dwell No. 1 interval.

As the step switch SS was stepped from step position 8 to step position 9, ground potential, i.e., L1 power, was applied through relay contacts CR4-1, switch SW-l,

phase A step switch contacts 884-8, and thence through phase B step switch contacts $84-10 to complete an energizing circuit through phase B switch SW-2 and phase B step switch driver coil CRS-C. Accordingly, this steps the phase B step switch SS from step position 10 to step position 11, the phase B red dwell No. 2 interval.

Phase A, step position 10 The red dwell No. 1 interval is a stop interval for phase A, as indicated by the chart in FIG. 4. The phase A unit will dwell in step position 10 until it becomes traffic actuated. As the phase A step switch SS was stepped from step position 9 to step position 10, L1 power was applied through contacts CR4-1 through phase A switch SW4, phase A step switch contacts 884-9, and thence in phase B unit through step switch contacts 884-11 and phase B switch SW-2 to complete an energizing circuit for the phase B step switch driver coil CRS-C. Thus, the phase B step switch is stepped from step position 11 to step position 1, the phase B special clearance No., 2 (stop) interval. Phase unit B is now in control and will commence timing its intervals No. 1 and No. 2 and then dwell in its green dwell interval, i.e., phase B step switch position No. 3, until it receives a call from phase A unit, indicative of a traffic actuation in phase A. The sequence of operation for phase unit B is the same as that just described with respect to phase unit A.

Although the invention has been described thus far in conjunction with a two phase, full actuated trafiic control system including separate phase units A and B for controlling trafiic flow through an intersection of trafiic actuated phases A and B, it is to be appreciated that the invention may also be used in conjunction with a semiactuated, two phase control system including a single control unit. More particularly, the phase unit A described thus far with respect to FIG. 3, may be converted to a two phase, semiactuated trafiic controller. This conversion takes place by merely opening switches SW-l, SW-2, SW-3, SW4 and SWS, and closing switches SW6 and SW7. In addition to actuating the switches, suitable load relay changes should bemade so that step switch SS connects both main street and cross street signal lamps to a source of power during the appropriate step switch intervals. Having made such conversions, a typical trafiic interval versus step position may take the form as shown in the chart of FIG. 4 (option 1) for a two phase, semiactuated controller. More particularly, it will be noted that step switch positions 10, 11 and 1 through 6 constitute a stop. period for main street trafiic, that step positions 7 and 8 serve as the main street go period, and that step position 9 serves as the main street caution or amber period. Also, under these conditions, it will be noted that step positions 6 through 11 and 1. serve as the cross street red or stop period, that step positions 2 through 4 serve as the cross street green or go period, and step position 5 serves as the cross street caution or amber period. As is common in the art of trafiic control for such a two phase, semiactuated controller, the cross street serves as the 'trafiic actuated phase and main street is the nonactuated traflic phase.

,The invention has been described in connection with a particular preferred embodiment, but is not to be limited to save. Various modifications may be made without departing from the scope and spirit of the present invention as defined by the appended claims.

Having thus described our invention, we claim:

1. A trafiic controller for controlling the operation of an intersection traffic signal displaying at least go and stop signals to at least two intersecting traflic phases, at least one of said phases being a trafiic actuated phase and to which a said go signal display includes an initial interval followed by a vehicle extension interval and which actuated phase has vehicle detection means associated therewith for developing a detection signal for each detected vehicle, said controller including for each said actuated phase:

minimum initial timing means for timing a predetermined minimum go signal initial interval and then developing a first signal;

variable initial timing means controlled by said associated detection means for timing a variable go signal initial interval in accordance with the number of vehicles detected by said detection means during the preceding period of time that a stop signal was displayed to said actuated phase and then developing a second signal;

vehicle extension timing means for timing a predetermined go signal vehicle extension interval and then developing a third signal;

starting means for concurrently energizing said minimum initial, variable initial, and vehicle extension timing means so that all of said timing means commence their timing functions at substantially the same point in time;

first AND circuit means for developing an initial interval termination signal only in response to concurrent occurrence of said first and second signals;

trafiic interval control means responsive to a said initial interval termination signal to terminate said go signal initial interval and allocate a said go signal vehicle extension interval;

second AND circuit means for developing a vehicle extension interval termination signal only when both said initial interval termination signal and said third signal have been developed; and,

said trafiic interval control means being responsive to a said vehicle extension interval termination signal to terminate a said go signal vehicle extension interval.

2. A trafiic controller as set forth in claim 1, including reset means controlled by said associated detection means for resetting said vehicle extension timing means in response to each detection of a vehicle in said actuated phase so that said vehicle extension timing means begins timing another said vehicle extension interval.

3. A tratfic controller as set forth in claim 2, including extension limit timing means for timing a predetermined time limit for said go signal display to said actuated phase and then developing a fourth signal;

reset disabling means responsive to a said fourth signal for disabling said reset means, whereby said vehicle extension timing means completes its timing function and develops said third signal.

4. A traffic controller as set forth in claim 3, including second starting means for developing an energizing signal for energizing said extension limit timing means.

5. A trafiic controller as set forth in claim 4, wherein said second starting means includes vehicle detection means associated with another of said phases, whereby said extension limit timing means is energized only in response to a vehicle detection occurring in another of said phases.

6. A traffic controller as set forth in claim 5, including third AND circuit means coupling said first and second starting means with said extension limit timing means.

7. A traffic controller as set forth in claim 1, wherein said controller is a semiactuated two phase controller.

8. A traffic controller as set .forth in claim 1, wherein said controller is a two or more phase traffic actuated controller and wherein for at least one of said phases said controller includes a semiactuated two phase controller having switching means for converting same to a single phase trafiic actuated control unit.

9. A traffic controller as set forth in claim 8, wherein said controller includes a said single phase trafiic actuated control unit for each phase.

10. A traffic controller as set forth in claim 1, wherein each of said timing means includes generating means for generating a timing signal which progressively varies in value with elapsed time, and comparing means for comparing said timing signal with a reference signal and developing an output signal when said timing signal and said reference signal attain a predetermined relationship to each other.

11. A traffic controller as set forth in claim 10, including means for providing said reference signal to said comparing means as a voltage potential.

12. A traflic controller as set forth in claim 11, wherein said timing signal is a voltage potential, and said comparing means includes a differential amplifier for comparing said potentials.

13. A traffic controller as set forth in claim 11, wherein said reference signal providing means is adjustable, whereby the time delay between energization of said generating means and development of a said output signal by said comparing means is directly proportional to the adjusted value of said reference signal.

14. A traffic controller as set forth in claim 10, wherein said generating means is a linear ramp function generating means for developing said timing signal so that it progressively varies in value in a linear manner with elapsed time.

15. A control system for controlling stop and go movement of movable means through an intersection of at least two flow paths of movement of said movable means, at least one of said flow paths having detection means associated therewith for detecting each said movable means in said one path, said system having for at least said one path:

first timing means for timing a predetermined minimum period of movement time along said one path for said movable means, and then developing a first signal;

second timing means for timing a variable period of movement time along said one path for said movable means in accordance wtih the number of said movable means detected by said detection means during a preceding period of time that go movement through said intersection was denied to movable means in said one path, and then develop ing a second signal;

third timing means for timing a predetermined go movement extension period of time and then developing a third signal;

starting means for concurrently energizing said first,

second, and third timing means so that all of said timing means commence their timing functions at substantially the same point in time;

fiirst AND circuit means for developing an initial go movement termination signal only in response to concurrent occurrrence of said first and second signals;

movement control means responsive to a said initial go movement termination signal to initiate termination of a first go movement period through said intersection and allocate an extension go movement period through said intersection;

second AND circuit means for developing an extension go movement termination signal only when both said initial go movement termination signal and said third signal have been developed; and,

said movement control means being responsive to a said extension go movement termination signal to terminate a said extension go movement period.

THOMAS B. HABECKER, Primary Examiner US. Cl. X.R.