GB1004417A - Improvements in or relating to apparatus for indicating or responsive to road traffic conditions - Google Patents

Abstract

1,004,417. Indicating road occupancy. DECCA Ltd. July 19, 1963 [April 19, 1962; Dec. 11, 1962], Nos. 28331/63 and 46799/62. Divided out of 1,004,416. Heading G4Q. [Also in Division G1] Apparatus for sensing vehicle speed comprises sensing means producing a signal of duration dependent on the time taken for the vehicle to travel a predetermined distance. As described, with reference to Fig. 2, the passage of a vehicle passing a detector of the electromagnetic or treadle type produces a pulse which energizes relay 22 changing over contacts 23 to allow capacitor 24 to charge to a potential dependent on the time the vehicle wheel takes to pass the detector. At the end of the time period relay 29 is operated by the differentiated pulse to discharge capacitor 24 into capacitor 31. The voltage across capacitor 31 is then indicative of the mean traffic speed. Relay 22 is a slow release relay to allow capacitor 31 time to change. In an alternative, Fig. 3, a transfer capacitor 41 is first charged from capacitor 24 and then used to charge capacitor 31. In a further embodiment, Fig. 4, two spaced sensing devices 51, 52 are used producing different amplitude pulses. Pulses from the first set a bi-stable circuit 59 which controls relay 22, and pulses from the second reset the bi-stable circuit and operate relay 29. A delayed reset device 60 is also provided to reset the bi-stable circuit in the event of the second sensing device not operating.