GB1250026A - Traffic light system - Google Patents

Abstract

1,250,026. Road signals for controlling traffic. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 20 Dec., 1968 [21 Dec., 1967], No. 60725/68. Heading G4Q. In a road traffic control system having two R.C. circuits R 1 C 1 , R 2 C 2 with different time constants interconnected by a rectifying element D 1 which becomes forward conducting when the charge acquired by the first capacitor C 1 substantially equals that acquired by the second capacitor C 2 , the capacitors C 1 , C 2 are discharged at the beginning of the green light period and the capacitor C 1 in the circuit of the lower time constant is maintained in a discharged state for a determined period of time, after which this capacitor C 1 starts to charge but is discharged instantaneously at the passage of a vehicle passing a vehicle sensing device on the road to which the green signal has been given, whereas the other capacitor C 2 is charged constantly so that the green prolongation time, after the minimum green time, is terminated when the voltage across the capacitor C 1 attains a given value in accordance with the traffic volume. As shown capacitance C 2 is higher than C 1 and contacts I close to instantaneously discharge C 1 when a vehicle is detected. When the voltage across C 1 becomes greater than C 2 , diode D conducts and the charge rate increases to R 1 (C 1 + C 2 ) so that if no vehicle passes, the extension of the green time is quickly terminated.