VEHICLE LOCATOR SYSTEM
First Claim
1. A system for monitoring the locations of a plurality of vehicles within a prescribed area, said system comprising:
- a plurality of signal transmitter means, one each carried by a respective one of said plurality of vehicles, for continuously emitting signals which are individually coded to identify the vehicle from which the emitted signal originates;
a plurality of sensor stations disposed at preselected locations within said prescribed area, each sensor station including means for receiving emitted signals from respective vehicles located within a predetermined distance from that sensor station and for providing a receiver output signal in response to each emitted signal received, said receiver output signal being coded to identify the vehicle from which that emitted signal was received;
decoder means responsive to application thereto of a receiver output signal for providing a digital signal which is coded to identify the respective applied receiver output signal;
scanning means for continuously and sequentially scanning said sensor stations and applying receiver output signals appearing at a station being scanned to said decoder means; and
data processing means synchronized with said scanning means and responsive to said digital signals for storing information representing the location of said plurality of vehicles, said information relating each vehicle to the respective sensor station which was the most recent sensor station to receive the emitted signal from that vehicle.
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Abstract
A system for automatically locating vehicles within a prescribed area utilizes an emitter comprising a coded transmitter device carried by each vehicle, a plurality of sensor stations disposed at preselected locations within the prescribed area for receiving vehicle identification-coded signals from nearby vehicles, a vehicle identification decoder for processing of coded signals received by the sensor stations, and a digital computer for processing decoded information to locate each vehicle on the basis of which sensor station most recently received that vehicle'"'"''"'"'s coded signal. The system may be utilized for police car location, whereby existing police call boxes may be utilized as sensor stations, and wherein a display map is provided on which lamps are lighted to indicate the presence of a police car sufficiently close to a call box to have its signal received thereby. Apart from the identification code, additional coded information may be emitted indicating vehicle status (i.e., fully loaded bus, for example, in a bus locator system) or emergency situations.
170 Citations
35 Claims
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1. A system for monitoring the locations of a plurality of vehicles within a prescribed area, said system comprising:
- a plurality of signal transmitter means, one each carried by a respective one of said plurality of vehicles, for continuously emitting signals which are individually coded to identify the vehicle from which the emitted signal originates;
a plurality of sensor stations disposed at preselected locations within said prescribed area, each sensor station including means for receiving emitted signals from respective vehicles located within a predetermined distance from that sensor station and for providing a receiver output signal in response to each emitted signal received, said receiver output signal being coded to identify the vehicle from which that emitted signal was received;
decoder means responsive to application thereto of a receiver output signal for providing a digital signal which is coded to identify the respective applied receiver output signal;
scanning means for continuously and sequentially scanning said sensor stations and applying receiver output signals appearing at a station being scanned to said decoder means; and
data processing means synchronized with said scanning means and responsive to said digital signals for storing information representing the location of said plurality of vehicles, said information relating each vehicle to the respective sensor station which was the most recent sensor station to receive the emitted signal from that vehicle.
- a plurality of signal transmitter means, one each carried by a respective one of said plurality of vehicles, for continuously emitting signals which are individually coded to identify the vehicle from which the emitted signal originates;
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2. The system according to claim 1 wherein said transmitter means each includes means for continuously providing a radiofrequency carrier signal, at least one coding frequency signal generator and modulator means for modulating said carrier signal with said coding frequency signal to provide the identification coding of said emitted signal.
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3. The system according to claim 2 wherein each transmitter means includes P coding frequency signal generators for providing P different identification coding frequencies, the combination of P coding frequencies being different at each of said transmitter means, there being N possible identification coding frequencies available for use by all said vehicles, N being greater than P, all N coding frequencies being geometrically spaced such that no coding frequency has either a second or third harmonic relationship with any other coding frequency, and wherein said modulator means includes means for modulating said carrier signal with said P coding frequency signals.
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4. The system according to claim 3 wherein said coding frequencies all fall in the audio frequency range and wherein said modulator means comprises an amplitude-modulator.
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5. The system according to claim 4 wherein said sensor stations each include amplitude-modulation receiver means responsive to reception of an emitted signal from a vehicle for detecting the audio tone coding frequencies which modulate the emitted signal;
- wherein said scanning means includes means for sequentially applying the detected audio tones from all said sensor stations to said decoder means;
wherein said decoder means includes a bank of filters having respective filter sections tuned to each of said N coding frequencies, each filter section having detector means connected thereto for providing a binary signal at a first level in response to passage of an audio tone through said filter section and at a second level when no audio tone is passed through said filter section, the binary signals provided by all said detector means comprising said digital signaL.
- wherein said scanning means includes means for sequentially applying the detected audio tones from all said sensor stations to said decoder means;
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6. The system according to claim 5 wherein the signals emitted by said transmitter means are additionally selectively codable to represent status conditions of the vehicle from which each emitted signal originates, said status conditions being represented by respective combinations of N'"'"''"'"' audio tone coding frequencies amplitude-modulating said radio frequency carrier, said N'"'"''"'"' coding frequencies being geometrically spaced relative to each other and to said N identification coding frequencies such that none of the N + N'"'"''"'"' coding frequencies have a second or third harmonic relationship to any other of said N + N'"'"''"'"' coding frequencies, wherein said bank of filters includes additional respective filter sections tuned to each of said N'"'"''"'"' status coding frequencies, and wherein each of said additional filter sections have a detector means connected thereto for providing a binary signal at a first level in response to passage of an audio tone through said filter section and at a second level when no audio tone is passed through said filter section, the binary signal provided by said last mentioned detector means comprising part of said digital signal, and wherein said data processing means includes means for storing status information for said vehicles.
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7. The system according to claim 6 is further comprising display means responsive to said data processing means for indicating each sensor station corresponding to a last-reported location of a vehicle, and for indicating status information of said vehicles at their respective last-reported locations.
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8. The system according to claim 7 wherein said display means comprises a map of said prescribed area, the location of each of said sensor stations being represented on said map by a first lamp which is lighted when that sensor station is the last-reported location of one of said vehicles, at least one additional lamp being provided at each sensor station location on said map to represent said at least one status condition of each vehicle whose last-reported location is that sensor station.
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9. The system according to claim 6 further comprising a display means responsive to said data processing means for indicating each sensor station corresponding to a last-reported location of a vehicle.
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10. The combination according to claim 9 wherein said display means comprises a map of said prescribed area, each of said sensor stations being represented on said map by a lamp which is lighted when that sensor station is the last-reported location of one of said vehicles.
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11. The system according to claim 1 wherein each vehicle further carries means for selectively transmitting a signal indicative of an emergency status.
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12. The system according to claim 1 wherein said transmitter means includes means for selectively coding said emitted signal to represent at least one status condition of the vehicle from which the emitted signal originate.
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13. The system according to claim 1 wherein said prescribed area is at least a portion of a city and wherein said sensor stations are street-side installations.
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14. The system according to claim 13 wherein said plurality of vehicles are police vehicles and wherein said sensor stations are police call boxes.
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15. The combination according to claim 14 wherein each emitted signal is a radio frequency carrier signal amplitude-modulated by respective multiple coding frequencies to provide identification coding of each emitted signal, wherein said sensor stations each include amplitude-modulation receiver means responsive to reception of an emitted signal from a vehicle for detecting the coding frequencies which modulate the emitted signal, wherein said scanning means sequentially applies the detected coding frequencies from all said sensor stations to said decoder means, and wherein said decoder means is located in a police precinct house, transmission of said detected coding frequencies from Said police call boxes to said precinct house being accomplished over telephone lines.
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16. The system according to claim 15 further comprising display means responsive to said data processing means for indicating each sensor station corresponding to a last-reported location of a vehicle.
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17. The combination according to claim 16 wherein said coding frequencies are audio tones, wherein each vehicle has a unique combination of P different identification coding frequencies, there being N possible coding frequencies available for use by all said police vehicles, all N coding frequencies being geometrically spaced so that no coding frequency has a second or third harmonic relationship with any other coding frequency.
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18. The combination according to claim 17 wherein each of said police vehicles is equipped with a two-way radio system having transmitter independent of said transmitter means, and further comprising emergency means for selectively amplitude-modulating the carrier frequency of the two-way radio transmitter with the coding frequencies of said transmitter means.
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19. The combination according to claim 13 wherein said plurality of vehicles are public buses.
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20. The system according to claim 7 wherein said prescribed area is at least a portion of a city, and wherein said sensor stations are street-side installations.
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21. The system according to claim 3 further comprising means for intermittently pulsing said transmitter means of each vehicle at a random rate whenever that vehicle is stopped to prevent interfering reception of emitted signals from two or more stopped vehicles at a single sensor station.
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22. The system according to claim 3 further comprising means for intermittently pulsing said transmitter means of each vehicle at a specified rate whenever that vehicle is traveling below a predetermined speed.
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23. The system according to claim 5 further comprising identification code verification means responsive to said digital signal for monitoring the number of binary signals therein at said first level and for rejecting said digital signal to prevent processing thereof whenever the number of binary signals at said first level is less than or greater than P. 24 The system according to claim 5 further comprising memory means for storing the digital signals provided in response to scanning of each sensor station until that sensor station is scanned again in sequence, and comparator means for providing as said digital signal only those binary signals which are identical upon successive scans of the same sensor station.
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25. The system according to claim 25 further comprising identification code verification means responsive to said digital signal for monitoring the number of binary signals therein at said first level and for rejecting said digital signal to prevent processing thereof whenever the number of binary signals at said first level is less than or greater than P.
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26. A system for monitoring the location of at least one vehicle within a prescribed area, said system comprising:
- transmitter means carried by said at least one vehicle for continuously emitting a relatively low power repetitive radio frequency signal;
a plurality of sensor stations disposed at preselected locations within said prescribed area, each sensor station including receiver means for receiving said radio frequency signal when emitted from a location within the receiving range of that sensor station, said sensor stations being spaced sufficiently that said vehicle is in the receiving range of only one sensor station at a time regardless of the location of said vehicle within said prescribed area, said sensor stations further including means for providing an output signal when said relatively low power radio frequency signal is received by said receiver means; and
scanning means for continuously and sequentially scanning said sensor stations to detect the presence of an output signal thereat, the rate of scanNing said sensor stations being selected to prevent said vehicle, travelling at its maximum speed, from passing through the receiving range of a sensor station between successive scans of that sensor station.
- transmitter means carried by said at least one vehicle for continuously emitting a relatively low power repetitive radio frequency signal;
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27. The method of tracking the location of a movable object within a prescribed area, said method comprising the steps of:
- a. continuously emitting from said object a repetitive identification signal uniquely representative of said object;
b. receiving said identification signal at a plurality of spaced locations with said prescribed area, the power of said identification signal being sufficiently low and the spacing between said spaced locations being sufficiently great to normally prevent more than one spaced location at a time from receiving said identification signal; and
c. indicating which of said spaced location most recently received said identification signal.
- a. continuously emitting from said object a repetitive identification signal uniquely representative of said object;
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28. The method according to claim 28 including the step of scanning said spaced locations in continuous sequence to detect reception of said identification signal thereat.
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29. The method according to claim 28 wherein said movable object is a vehicle, and wherein said method is employed to track the locations of a plurality of vehicles within said prescribed area, wherein each vehicle continuously emits an identification signal uniquely representative of that vehicle.
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30. The method according to claim 29 wherein the step of continuously emitting comprises, for each vehicle, the steps of:
- generating a low power radiofrequency carrier signal;
generating P audio tones at different frequencies, each vehicle generating a unique combination of audio tones; and
amplitude modulating said carrier signal with said audio tones to provide said identification signal.
- generating a low power radiofrequency carrier signal;
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31. The method according to claim 30 wherein said P audio tones are selected from N possible audio tones, the frequencies of said N audio tones being geometrically spaced such that none of the N audio tones have second and third harmonic relationships with one another.
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32. The method according to claim 30 further comprising the steps of:
- monitoring the number of audio tones which are amplitude-modulating each of said received identification signals; and
rejecting all received identification signals which are amplitude-modulated by a number of audio tones not equal to P.
- monitoring the number of audio tones which are amplitude-modulating each of said received identification signals; and
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33. The method according to claim 29 further comprising the step of selectively coding said identification signal at each vehicle to represent a status condition for that vehicle.
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34. The method according to claim 29 further comprising the step of storing at the location of each vehicle the last spaced location to receive the identification emitted from said each vehicle.
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35. The method according to claim 29 further comprising the step of automatically pulsing said identification signal of each vehicle on and off whenever the speed of that vehicle is below a predetermined speed.
Specification