Patent GB-983285-A (GB)
Title: Improvements in or relating to vehicle actuated traffic signal systems
Inventor: POPE JOSEPH
IPC: G08G1/09
Filed: 1960-12-17
Abstract: 983, 285. Road traffic control systems. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. Sept. 26, 1961 [Dec.17, 1960], No. 43510/60. Heading G4Q. A vehicle actuated traffic signal system including an arrangement for detecting the speed of the vehicle comprises a speed discriminating circuit including two capacitors, one of which is charged to a predetermined value representative of a maximum permissible speed whereas the other is charged under the control of the speed detecting arrangement to an extent representative of the detected speed of the vehicle. Arrangements are provided for comparing the two charges so that if the charge on the other capacitor exceeds the charge on the one capacitor a signal is generated indicating that the speed of the vehicle exceeds the maximum permissible speed. This signal is used to control at least one indicating lamp adjacent the highway. An array of display lanterns at the approach to a hazardous section of road consists of an illuminated speed limit SLS, followed further along the road by a display SDS signifying slow down, and a flashing light FS, both operated when a vehicle passes a detection point at excessive speed. The detector may be of the form wherein two contacts DCA, DCB are operated successively by treads in the road surface by vehicles moving in the direction shown. The operation of the contacts actuates a relay A, and then a relay B, whereupon the operation of a contact B1 causes the relay A to be held on by the contacts A1 until the contacts DCB are opened again. In the circuit of the valve V1 the differential relay X normally conducts so as to hold a contact X1 closed, and the right side of a condenser C1 and the left side of a condenser C2 are charged to respectively higher and lower positive potentials. With the actuating of the relay A, the contact A3 is altered so that C1 commences to discharge through a resistor chain R2-R5 set according to the speed limit in force. When the relay B operates, the contact B3 opens to prevent further discharge, the contact B4 alters to connect C1 to C2 so that any positive difference in potential between C1 and C2 is applied to the grid of V1 as a pulse and the contact B2 opens so as to reduce the current through the left hand side of the differential relay X (the contact A2 is already open). If a positive pulse is transferred from C1, corresponding to the passage of a vehicle travelling in excess of the speed limit, the increase in current through the valve V1 actuates the differential relay X. This brings into operation the contacts X2 causing the relay Y to operate and thus closing the circuit of SDS and actuating the rotating contact CC so as to cause FS to flash. When the vehicle has cleared the detector, the relay D releases, thus initiating the release of the relay A. The relay Y remains actuated until the delay circuit involving the condenser C3 and the valve V2 allows the release of the relay, whereupon the lanterns SDS and FS are disconnected and all the relays return to their normal settings. Specification 653,900 is referred to.