GB1378689A - Vehicle monitoring systems - Google Patents

Abstract

1378689 Vehicle monitoring system SPERRY RAND CORP 22 Feb 1972 [12 March 1971] 8047/72 Heading G4H [Also in Divisions H3 and H4] A vehicle monitoring system for signalling at a central station the presence of co-operating vehicles at predetermined locations comprises a transmitter at each location which continuously emits EM pulses at a pulse repetition frequency unique to its location, a receiver carried by each vehicle to derive a measure of the frequency of the received signal, and a transmitter mounted on each vehicle to transmit a representation of the frequency measure to the central station so as to identify the vehicle location at the moment of transmission. The location transmitters may be incorporated in lamp posts at suitable street corners, Figs. 1, 2 (not shown); they employ transmission line systems for propagating TEM waves (see Divisions H3-H5). Signals from such a transmitter are received by an omnidirectional bicone antenna 8 on the roof 6a of a vehicle and fed via a highpass filter 65 to a detector circuit comprising a tunnel or other suitable diode 69; each incoming signal pulse causes the diode to become highly conductive. Current pulses of greater amplitude and longer duration than the input pulses are generated by the diode and fed to a monostable circuit 70; pulses from 70 pass through a gate 72 to a counter 73, the trailing edge 71 of each pulse serving to reset diode 69 for the next pulse. Gate 72 is opened for a predetermined time at regular intervals by an interrogator 78 (a pulse generator operated by a clock signal, by the vehicle operator or by a command signal from the central station), and the pulse count accumulated in 73 is directly transmitted to the central station by the vehicle voice radio communication link, or fed to an encoder 74 which causes transmission of a pulse coded signal which automatically identifies the particular vehicle as it reports its location.