Vehicle locating system with Loran-C
First Claim
1. A method of locating a vehicle equipped with a receiver for low frequency radio waves in response to first pulses of said low frequency radio wave transmitted to the vehicle from three stations having known locations, the first pulses being transmitted from the stations at precise time intervals so that the pulses from the different stations arrive at the vehicle at displaced times, the method comprising receiving the first pulses of the low frequency radio waves at the receiver on the vehicle, transmitting from the vehicle a radio frequency wave modulated by second pulses having displaced time positions synchronized and corresponding with the reception times of the first pulses as received by the receiver, receiving the radio frequency wave at a location displaced from the vehicle, detecting the displaced time positions of the second pulses in response to the radio frequency wave received at the location displaced from the vehicle, and determining the location of the vehicle from the detected displaced time positions.
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Accused Products
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.
155 Citations
36 Claims
- 1. A method of locating a vehicle equipped with a receiver for low frequency radio waves in response to first pulses of said low frequency radio wave transmitted to the vehicle from three stations having known locations, the first pulses being transmitted from the stations at precise time intervals so that the pulses from the different stations arrive at the vehicle at displaced times, the method comprising receiving the first pulses of the low frequency radio waves at the receiver on the vehicle, transmitting from the vehicle a radio frequency wave modulated by second pulses having displaced time positions synchronized and corresponding with the reception times of the first pulses as received by the receiver, receiving the radio frequency wave at a location displaced from the vehicle, detecting the displaced time positions of the second pulses in response to the radio frequency wave received at the location displaced from the vehicle, and determining the location of the vehicle from the detected displaced time positions.
- 10. Apparatus adapted to be mounted on a vehicle for (a) responding to (i) first radio waves having a low frequency modulated by first pulses, the first radio waves being derived by at least three sources at known different locations, (ii) a signal indicating a sensed condition of the vehicle, and (iii) another wave having a predetermined code, and (b) transmitting a second radio wave to a remote receiver, the apparatus comprising means responsive to the another wave having the predetermined code for deriving a disabling signal, a receiver for the pulse modulated low frequency radio waves, means responsive to the receiver for deriving a second radio wave modulated by second pulses having displaced time positions synchronized and corresponding with the reception times of the first pulses as received by said receiver, and means responsive to the sensed condition signal and the disabling signal deriving means for selectively transmitting the second radio wave to the remote receiver.
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14. A system for determining the location of a vehicle at a location remote from the vehicle, said vehicle being assigned a serial number, said system being responsive to Loran-C emissions from at least three Loran-C transmitters, said system comprising a central master station, plural local networks, each of said local networks including a local master station in a bi-directional communication link with the central master station, each of said vehicles including:
- means for receiving the Loran-C emissions, the means for receiving the Loran-C emissions deriving pulses having time positions corresponding with and synchronized with Loran-C pulses as received by the means for receiving, a transmitter responsive to the means for receiving for modulating a first carrier having a frequency much higher than the Loran-C emissions with further pulses having time positions corresponding with and synchronized with Loran-C pulses as received by the means for receiving, and a receiver for a second carrier having a frequency much higher than the Loran-C emissions;
the first and second carriers being transmitted via radio links to the local master station in proximity to the vehicle;
the local master station including;
means responsive to the first carrier for detecting the time difference between sets of the further pulses modulating the first carrier, means responsive to the time difference detecting means for determining the vehicle position, and means responsive to the vehicle position determining means and the first carrier for transmitting a data signal to the central master station indicative of the determined vehicle position and the vehicle serial number;
the central master station including;
means responsive to the data signal for indicating the vehicle location and serial number, means for transmitting an information signal including the serial number for one of the vehicles to said master local stations, each of said local master stations including a receiver for the information signal and means for modulating the second carrier with the information signal;
the receiver of one of the vehicles including means for detecting the information signal assigned to said one vehicle. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
- means for receiving the Loran-C emissions, the means for receiving the Loran-C emissions deriving pulses having time positions corresponding with and synchronized with Loran-C pulses as received by the means for receiving, a transmitter responsive to the means for receiving for modulating a first carrier having a frequency much higher than the Loran-C emissions with further pulses having time positions corresponding with and synchronized with Loran-C pulses as received by the means for receiving, and a receiver for a second carrier having a frequency much higher than the Loran-C emissions;
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22. A security system for a vehicle comprising a code generator for emitting a first wave coded for the vehicle, the vehicle including:
- sensor means for a condition of the vehicle, a receiver for the first wave, a low frequency receiver for Loran-C emissions, a transmitter for radio frequency waves, and means responsive to the receiver for the first wave, the low frequency receiver and the sensor means for controlling activation of the radio frequency transmitter so that replicas of Loran-C pulses received by the low frequency receiver selectively modulate the radio frequency waves transmitted by the radio frequency wave transmitter.
- View Dependent Claims (23, 24, 25, 26, 27, 28)
- 29. A local master station comprising a receiver for a radio wave modulated with a coded signal indicative of a serial number of a vehicle and with replicas of Loran-C pulses as received by the vehicle, means responsive to the replicas of the Loran-C pulses for calculating the location of the vehicle, and means responsive to the coded signal and the means for calculating for transmitting to a central station a wave including the coded signal indicative of the vehicle serial number and a signal indicative of the calculated vehicle location.
- 32. Apparatus adapted to be mounted on a vehicle to (a) be responsive to (i) first radio waves having a low frequency modulated by first pulses, the first radio waves being derived by at least three sources at known different locations, and (ii) another wave having a predetermined code, and (b) transmit a second radio wave to a remote receiver, the apparatus comprising, a first receiver for the pulse modulated low frequency first radio waves, a second receiver for the another wave, and means responsive to the first and second receivers for deriving the second radio wave, the second radio wave being modulated by second pulses having displaced time positions synchronized and corresponding with the reception times of the first pulses as received by said first receiver and modulated by a digital indication of a serial number for the vehicle.
Specification