Vehicle location system
First Claim
1. A vehicle location system for providing a remote site with updated information regarding vehicle location wherein a plurality of stationary low power wayside radio transmitter stations respectively transmit digitally encoded location messages indicative of their respective geographical locations, said vehicles each carrying a radio receiver for receiving said coded message when said vehicle is in the proximity of said transmitter, and a radio transmitter for transmitting digitally encoded location messages to said remote site, wherein the improvement comprises:
- means at each of said stationary wayside radio transmitter stations for accompanying said digitally encoded location messages with a first plurality of data bits preceding each digitally coded message and a second plurality of data bits following each digitally coded message, said first and second plurality of data bits encoding respectively different predetermined start and stop code patterns; and
signal verifier means carried by each of said vehicles and coupled to said radio receiver carried by the vehicle which receives the encoded location messages from the wayside transmitter stations, said signal verifier means comprising the comparing start and stop code patterns with stored code formats permanently retained in said signal verifier means, the same code formats being permanently retained in each of said vehicles;
said signal verifier means operatively coupled to said radio transmitter carried by the vehicle for inhibiting transmission of said digitally encoded location messages to said remote site unless the predetermined start and stop code patterns compare with said permanently retained code formats.
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Accused Products
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.
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Citations
15 Claims
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1. A vehicle location system for providing a remote site with updated information regarding vehicle location wherein a plurality of stationary low power wayside radio transmitter stations respectively transmit digitally encoded location messages indicative of their respective geographical locations, said vehicles each carrying a radio receiver for receiving said coded message when said vehicle is in the proximity of said transmitter, and a radio transmitter for transmitting digitally encoded location messages to said remote site, wherein the improvement comprises:
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means at each of said stationary wayside radio transmitter stations for accompanying said digitally encoded location messages with a first plurality of data bits preceding each digitally coded message and a second plurality of data bits following each digitally coded message, said first and second plurality of data bits encoding respectively different predetermined start and stop code patterns; and signal verifier means carried by each of said vehicles and coupled to said radio receiver carried by the vehicle which receives the encoded location messages from the wayside transmitter stations, said signal verifier means comprising the comparing start and stop code patterns with stored code formats permanently retained in said signal verifier means, the same code formats being permanently retained in each of said vehicles;
said signal verifier means operatively coupled to said radio transmitter carried by the vehicle for inhibiting transmission of said digitally encoded location messages to said remote site unless the predetermined start and stop code patterns compare with said permanently retained code formats. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a vehicle location system wherein stationary wayside stations are used to reference the locations of a plurality of vehicles at a given point in time and wireless paths subject to interference and substantial attenuation when any appreciable distance separates the vehicle from a wayside station are used for transmitting digitally encoded messages between said stationary wayside stations and said vehicles, the improvement for maintaining the integrity of said messages by detecting errors resulting from the interference and attenuation of said wireless path comprising:
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means for accompanying said digitally encoded messages with a predetermined digital code pattern, signal verifier means carried by each of said vehicles for comparing said predetermined digital code pattern with a fixed unchanging code format permanently retained in said signal verifier means, said same code format being permanently retained in each of said vehicles, and means responsive to said signal verifier means for inhibiting utilization of said digitally encoded messages unless the predetermined digital code pattern transmitted over said wireless path compares with said permanently retained code format. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A vehicle location system for providing a remote site with updated information regarding vehicle location wherein a plurality of stationary low power wayside radio transmitter stations respectively transmit digitally encoded location messages indicative of their respective geographical locations, said vehicles each carrying a radio receiver for receiving said coded message when said vehicle is in the proximity of said transmitter, and a radio transmitter for transmitting digitally encoded location messages to said remote site, wherein the improvement comprises:
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means at each of said stationary wayside radio transmitter stations for accompanying said digitally encoded messages with a first plurality of data bits preceding each digitally coded message and a second plurality of data bits following each digitally coded message, said first and second plurality of data bits encoding respectively different predetermined start and stop code patterns; signal verifier means carried by each of said vehicles and coupled to said radio receiver carried by the vehicle which receives the encoded location messages from the wayside transmitter stations, said signal verifier means comparing the predetermined start and stop code patterns with stored code formats permanently retained in said signal verifier means, the same code formats being permanently retained in each of said vehicles; a keyboard in said vehicle for selecting a predetermined message; means coupled to said radio transmitter for storing a vehicle designation, the keyboard selected message, and the digitally encoded location message; and means operatively coupling said signal verifier means to said radio transmitter carried by the vehicle for inhibiting transmission of said stored messages to said remote site unless the predetermined start and stop code patterns compare with said permanently retained code formats.
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15. A vehicle location system for providing a remote site with updated information regarding vehicle location wherein a plurality of stationary low power wayside radio transmitter stations respectively transmit digitally encoded location messages indicative of their respective geographical locations, said vehicles each carrying a radio receiver for receiving said coded message when said vehicle is in the proximity of said transmitter, a radio transmitter for transmitting digitally encoded location messages to said remote site, and a radio receiver for receiving messages from said remote site having a squelch system for providing an output signal indicative that the transmit-receive radio frequency channel between the vehicle and said remote site is clear, wherein the improvement comprises:
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means at each of said stationary wayside radio transmitter stations for accompanying said digitally encoded messages with a first plurality of data bits preceding each digitally coded message and a second plurality of data bits following each digitally coded message, said first and second plurality of data bits encoding respectively different predetermined start and stop code patterns; signal verifier means carried by each of said vehicles and coupled to said radio receiver carried by the vehicle which receives the encoded location messages from the wayside transmitter stations, said signal verifier means comparing the predetermined start and stop code patterns with stored code formats permanently retained in said signal verifier means, the same code formats being permanently retained in each of said vehicles;
said signal verifier means operatively coupled to said radio transmitter carried by the vehicle for inhibiting transmission of said digitally encoded location messages to said remote site unless the predetermined start and stop code patterns compare with said permanently retained code formats;means carried by each of said vehicles responsively coupled to said output signal of the squelch system of said receiver and operatively coupled to said radio transmitter for automatically delaying transmission of said digitally encoded location message to said remote site until the transmit-receive channel is clear; and means for transmitting both audio and digitally encoded messages over the same channel from said remote site to said vehicle including in each vehicle (i) an audio speaker coupled to said receiver for communicating said audio message and (ii) means coupled to said receiver and said speaker for detecting receipt of an encoded data signal at the vehicle and automatically disconnecting said speaker during transmission of said encoded data.
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Specification