| 摘要 |
<p>An integrated radio location and communication system comprising a plurality of radio locator-transmitter devices which may be fixed to vehicles and/or carried by persons and which are capable of transmitting the position and identity of the devices to two or more centrally located fixed receiver sites. The system provides a means of continuously locating and identifying the devices within a city-wide area, or in large subdivisions therein, for example, within a university campus. Each of the locator-transmitters is continuously phase-locked to the RF carrier of a nearby commercial broadcast station, which station is modified slightly to provide periodic transmission of a transmitter range-tone signal. An identical phase-locked range-tone signal is likewise generated within each locator-transmitter. The two or more centrally located fixed receivers detect the carrier range tone signal from the broadcast station and the transmitter range-tone signal from each locator-transmitter device, compares the phase difference between the signals and in response computes the location of each locator-transmitter device. The system is capable of continuously determining the location of hundreds of thousands of locator-transmitters and communicating automatically the position and identity information to two or more fixed receiver sites.</p> |
