Patent GB-1154131-A (GB)
Title: Traffic Control System.
Inventor: CABE RAY WALTER
IPC: G08G1/08
Filed: 1968-01-16
Abstract: 1,154,131. Road traffic signals. TAMAR ELECTRONICS INDUSTRIES Inc. 16 Jan., 1968, No. 2419/68. Heading G4Q. The phases of a traffic control system are timed by deriving one second clock pulses by frequency division from an A.C. mains supply (Fig. 2, not shown) and feeding them to a main timer comprising a two-stage decimal counter (Fig. 3, not shown) coupled to selector switches so that outputs are obtained at predetermined time intervals; a second similar counting system (Fig. 4, not shown) is used to time extensions. The system as a whole is regulated by a five-stage ring counter (113, Fig. 5, not shown) and a two-stage ring-counter (116, Fig. 5) which allots control alternately to the phase A controller and to the phase B controller. Main road (phase A) controller, Fig. 6.-In position 1 of the five-stage ring counter, the minimum green period, a signal is applied on line 127 to AND gate 124. When the main timer has timed this interval an output from gate 124 passes via OR gate 205 to advance the counter to position 2 and reset the main timer. Position 2 is a rest position where right-of-way is retained on the main road until there is a demand on the other route when a signal on line 130 causes AND gate 125 to respond. Positions 3-5 are timed by the main timer, and after position 5 control is transferred to the phase B controller. In positions 1-3 signals from OR gate 140 open AND gate 160 thereby energizing a switch device 170 which allows power to pass from the source 150 to the green signal 168. In position 3 the pedestrian warning signal 232 is energized, in position 4 the vehicle warning signal 180 is energized, and position 5 is an all red period due to the absence of inputs to OR gates 195 and 240. Minor road (phase B) controller (Fig. 7, not shown).-This is generally similar to the phase A controller. In position 1 an initial green period is timed by the main timer; position 2 is timed by the extension timer which is reset each time there is a demand, the total time being limited to a maximum timed by the main timer; position 3 is not used, position 4 is the vehicle amber period and position 5 the all red, after which control reverts to phase A. A vehicle demand which is ineffective is stored (in bistable 254, Fig. 9, not shown) and recalls control after the phase A cycle. Such a demand may be simulated by closing a manual switch (266, Fig. 9) thereby providing continuous cycling of the phases instead of vehicle control. Pedestrian-operated control, Fig. 8.-A switch 401 operated by a pedestrian in the absence of the green pedestrian signal is fed through AND gate 405 to set bi-stable 415 which registers a demand in the same way as a vehicle and thereby causes the phase A controller to complete its cycle. In position 1 of phase B control, an output from AND gate 420 sets bi-stable 411 which operates the switch device 422 for the pedestrian green signal 410 and re-sets bi-stable 415. The green period is timed by the extension timer which provides an output on line 430, and the period ends either at this time or when the phase B vehicle amber signal is energized, when a signal is present on line 450. Either input to gate 435 operates AND gate 440 which sets bi-stable 447 controlling the switch device 451 for the pedestrian warning signal 452. This warning period is ended either by a timing signal on line 460 or when the phase B vehicle red signal is energized, when a signal is present on line 472. Bi-stable 447 is then reset thereby energizing AND gate 380 which operates the switch device 470 controlling the pedestrian red signal 468. Switch 402 allows a demand to be simulated when continuous operation is required.