Vehicle location system

Abstract

A vehicle location system having a plurality of stationary wayside stations positioned at predetermined geographical locations. The passage of a vehicle near a station references the location of the vehicle at that point in time and automatically supplies the remote headquarters with updated information as to the whereabouts of all vehicles operating in the system. The system enables low power radio frequency signals to automatically communicate error free location information between the wayside station and the vehicle by maintaining the integrity of the signal. Automatic transmission to a remote headquarters of a precoded message such as an emergency communication can be initiated from either the vehicle or a portable transmitter. A common radio frequency channel may be used for transmittal of both audio and digitally encoded messages to and from a plurality of vehicles and a discriminator in each vehicle automatically selects and displays only those digital communications directed to it. Simultaneous automatic transmissions on the same radio frequency channel are avoided by delaying energizing the vehicle transmitter until the preselected channel is open. Unpleasant and distracting noise in the vehicle is minimized by turning off the audio speaker during reception of digitally encoded data.

Dependencies are inferred from the claim text.