Patent GB-802590-A (GB)
Title: Improvements in or relating to traffic light switching arrangements
IPC: G08G1/085
Filed: 1956-03-27
Abstract: 802,590. Road signals for controlling traffic. KIPS, E. J. E., and DERKSON, J. W. March 27, 1956 [April 1, 195.5]. No. 9576/56. Class 118 (2). A traffic-light switching arrangement is characterized in that the periodical switching of lights is effected by means of an uninterrupted series of pulses supplied to a plurality of discharge tubes connected in a closed pulsecounting circuit, which discharge tubes are adapted each to be rendered conductive by a different one of said pulses and upon becoming conductive to render the preceding tube non-conductive and to prime the subsequent tube for ignition by the subsequent pulse. For each traffic-light there is provided an electronic device connected with a selected one of the discharge tubes. Whenever its associated discharge tube becomes conductive this device provides a voltage for lighting its related traffic-light and for causing extinction of another traffic-light. The said discharge tubes and electronic devices may comprise thyratrons. The embodiment shown in the form of a block diagram comprises a pulse generator PG which supplies a pulse every three seconds. Forty-two thyratrons are ignited in turn by the pulses and are indicated by the reference numerals 0,3 ... 30, 33, 36 ... 97 ... 117, 120, 123 in accordance with the point of time of their ignition in each cycle. These thyratrons are connected in a known closed cyclic arrangement in which only one tube at a time is conductive. When a tube ignites a pulse is provided at the associated terminal k which may be connected to a load resistor in the tube cathode circuit (Fig. 2, not shown). Each of the traffic-lights R, Y and G (red, yellow and green, respectively), is series-connected with an electronic switching device such as thyratrons T1, T2 or T3, and these are controlled by discharge tubes I1, I2, I3, which are interconnected such that when one ignites it extinguishes the previous one. Each of the control grids of tubes I1, I2, I3 is connected by a cord to a selected terminal k. Thus, as shown, when the thyratron O is ignited the tube I1 is fired and the green light G is lit. After 33 seconds 12 is fired, extinguishing 11 and the green light G, and lighting yellow light Y. Three seconds later 12 is extinguished by 13 and the yellow light Y gives way to the red light R. This red light remains until 13 is extinguished by 11 which occurs after 90 seconds (126 less 36). A second set of trafficlights may be connected as shown on the right of the Figure. By arrangement of the cord connections it is possible to vary the periods within the total cycle time of 126 seconds, or to make two or more lighting cycles within this time by providing the tubes 11, 12, &c, with more than one cord for connection to two or more terminals k. Two or more different groups of traffic lights may be operated from the one closed pulse-counting circuit provided that the time of the cycle of such groups equals that of the counting circuit or a whole fraction thereof. The switching devices T1, T2, &c. may be in the primary circuits of transformers supplying the traffic-lights at low voltage and may each comprise two triode valves in parallel (as in Fig. 2, not shown), thereby facilitating operation at full voltage by day and half voltage at night.