GB1407619A - Electrical signal transmission systems - Google Patents

Abstract

1407619 Traffic light control systems SIEMENS AG 29 Sept 1972 [30 Sept 1971] 45016/72 Headings G4H and G4Q A signal transmission system comprises a central station I, XI, XXI which transmits control pulse trains to remote stations Kr 1 , Kr 11 , Kr 21 , a common timing pulse generator Tg in the central station and a control channel L 1 , L 11 , L 21 for each remote station, the control pulses having an effect on the remote stations dependent on their time position within cyclically repeated pulse groups generated by the pulse generator. The system enables the control of traffic lights at road intersections which form the remote stations, each intersection including four pairs of red and green lights in units Sg1-Sg4. The central station includes a computer Z provided with a programmer Pg which generates sequences of four control pulses. When the pulse generator Tg is operated a transmitter S transmits sequences of eight timing pulses to receivers E1, E1 11 , E1 21 which cause switch arms e1 1 , e1 2 , &c. to step once for each timing pulse. If a control pulse is received via a transmitter such as S2 1 simultaneously with a timing pulse, a contact e2 1 is closed by a receiver E2 1 and that bi-stable relay S1-S4 selected by the instantaneous position of the arm e1 1 is operated. The relays control switches S1-S4 to energize a red or green light in the units Sg1-Sg4. Monitoring relays K1- K8 having contacts k1-k8 supply an acknowledgement signal via a transmitter S3 1 and a receiver E3 1 to the central station. If the operated light does not correspond to that commanded by the programmer Pg, a contact e3 1 remains closed when a contact p is closed by a relay P so that a relay A is energized to close its contact a and operate an alarm bell W. Different frequencies are used for the control pulses, the timing pulses and the acknowledgement signals. In a modification the timing signals consist of 4-bit words to define sequences of six successive time slots. The timing signals are decoded at the remote intersections and enable the control pulses to control nine groups of three traffic lights at each intersection.