Vehicle location system

Claim 2

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.

Claim 3

In the vehicle location system of claim 1 which includes: a radio transmitter carried by each vehicle for transmitting over a radio channel said updated information regarding vehicle location to said remote site, a radio receiver tuned to the channel over which said messages are transmitted to said remote site, and means responsively coupled to said receiver for automatically delaying transmission of an encoded message to said remote site until said channel is clear.

Claim 4

In the vehicle location system of claim 2 wherein: said radio receiver includes a squelch system for providing an output signal indicative that said channel is clear, and means responsive to said output signal for inhibiting transmission of said encoded message to headquarters until said signal is received.

Claim 5

In the vehicle location system of claim 1 including: portable transmitter means for transmitting a radio frequency signal over the same channel as said radio frequency communication links between said wayside stations and vehicles, and means independent of said signal verifier means responsive to the signal from said portable transmitter means for automatically initiating a predetermined encoded message from said vehicle to said remote headquarters.

Claim 6

In the vehicle location system of claim 4 wherein: said portable transmitter includes a source of clock pulses and timer means for modulating the portable transmitter with said clock pulses for a predetermined length of time, and said means responsive to said portable transmitter signal uniquely responds to a continuous series of said pulses for a predetermined period of time somewhat less than the interval during which pulses are transmitted for said portable transmitter.

Claim 7

In the vehicle location system of claim 1 wherein both audio and digitally encoded messages may be sent from another site to said vehicle, the system including: an audio speaker carried by a vehicle for communicating said audio messages, means for minimizing the noise which would otherwise be produced by said digital data in said audio speaker including, first means responsive to receipt of an encoded data signal at said vehicle, and second means responsive to said first means for disconnecting said audio speaker during transmission of said encoded data.

Claim 8

In the vehicle system of claim 6 wherein said digitally encoded messages sent to said vehicle from another site are preceded by a tone of predetermined frequency, said system including: a tuned high Q resonant circuit responsive to said predetermined tone frequency, and switch means responsive to said resonant circuit for disconnecting said audio speaker.

Claim 9

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: 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.

Claim 10

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: 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.

Claim 11

In the vehicle location system of claim 8 wherein: said predetermined digital code pattern comprises a plurality of data bits preceding each digitally coded message, so that errors induced by noise in said wireless path during the initial portion of transmission over said wireless path will be detected in said signal verifier means.

Claim 12

In the vehicle location system of claim 8 wherein: said predetermined digital code pattern comprises a plurality of data bits following each digitally coded message, so that errors induced by noise in said wireless path during the latter portion of transmission over said wireless path will be detected in said signal verifier means.

Claim 13

In the vehicle location system of claim 8 wherein: said signal verifier means includes means for registering the digital code pattern which accompanies said digitally coded message, and means for converting said registered code pattern to the same format as said permanently retained code format.

Claim 14

In the vehicle location system of claim 11 wherein: said permanently retained code format is a number in the decimal system, and said means for converting said registered code format comprises a binary-to-decimal converter which provides an output transmit enable signal only when the decimal value encoded by said accompanying bits corresponds to said decimal number stored in said converter means.

Claim 15

In the vehicle location system of claim 8 which includes: means responsive to said signal verifier means for automatically retransmitting said digitally encoded message upon receipt of a transmit enable signal from said signal verifier means.

Claim 16

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 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.

Claim 17

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 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.

Claim 18

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: 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.

Claim 19

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: 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.