| 摘要 |
<p>BROADCAST SYNCHRONIZATION /A SUPERVISION SYSTEM A system is disclosed which employs existing broadcast stations to transmit synchronizing and supervisory signals for use by telephone communication devices at remote locations for timing purposes and for coordinating their activities with acivities at other locations. The system comprises a broadcast transmitter modified to transmit phase (or frequency) modulated digital signals, which digital signals are synchronized to the carrier of the broadcast station. The broadcast station includes equipment to both periodically transmit synchronizing and supervising signals to coordinate activity of remote devices, and to transmit messages to them. The messages are generated at a central computer location and conveyed to the broadcast station by a dedicated phone line, a microwave link, or other known methods. At remote locations a TELRAD modem includes a radio receiver to detect the broadcast signals which synchronize and supervise them and associated customer apparatus. A central control computer generates the messages. Communications to and from remote monitoring locations is also accomplished. Another important object is to provide broadcast transmissions from more than one broadcast station by providing a receiver at secondary broadcast stations tuned to the primary master transmitter, which receiver detects the transmissions of the master transmitter, modulates the repeater transmitter in the prescribed manner and retransmits the signal to extend the service area.</p> |
