Importance

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Abstract

Improvements are provided for a vehicle locator system of the type in which vehicle-borne emitters radiate coded tone combinations for reception by spaced sensors which are linked to a central decoding office. In one improvement the vehicle capacity of the system is increased without increasing the number of tone oscillators by using a sequential tone coding arrangement wherein each oscillator is switchable to provide a different tone during different intervals in the coding sequence. In addition, the pulsing rate of the emitted tone is synchronized to the vehicle odometer to assure that a code sequence is transmitted while the vehicle is in the proximity of each sensor station. Additional modifications include party line sharing of telephone lines connecting the sensors to the decoder, the use of long-distance telephone connections to provide coverage for large geographie regions, the use of radio call boxes to link the sensors to a decoding station, and delaying emitter pulsing when two vehicles are in close proximity to reduce the possibility of simultaneous reception of two vehicle codes at a sensor station.

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First Claim