Importance

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Abstract

The location of a vehicle having an assigned serial number is determined at a location remote from the vehicle with a system including a central master station and plural local networks, each having a local master station in a bi-directional communication link with the central master station. Each vehicle includes a receiver for Loran-C emissions, a transmitter for modulating a first carrier having a frequency much higher than the Loran-C emissions with pulses having time positions corresponding with and synchronized with Loran-C pulses as the received Loran-C emissions, and a receiver for a second carrier having a frequency much higher than the Loran-C emissions. The first carrier is modulated by vehicle serial number signals. The carriers are transmitted via radio links between the local master station and vehicle. The local master station responds to the first carrier to detect the time difference between pulses modulating the first carrier to determine vehicle position. A data signal transmitted by the local master station to the central master station indicates the vehicle position and serial number. The central master station responds to the data signal to indicate vehicle location and serial number. The central master station transmits an information signal including a vehicle serial number to the local master stations. The central master station derives a voice signal that is converted to an aural signal at the vehicle with the designated serial number. The vehicle includes a receiver for a locally generated vehicle identification signal vehicle condition sensors. Activation of the transmitter on the vehicle is controlled in response to the receiver for the locally generated coded signal and the sensed vehicle conditions, and in response to the serial number signal originating at the central master station.

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First Claim