| 摘要 |
A radio calling system comprises a plurality of service areas (6) each with local exchange (1,2, 3, 4 or 5) and respective transmitters (e.g.7 to 13) synchronised by signals from local exchange (2) and working in synchronous common carrier frequency broadcast operation. To ensure maintenance of high frequency synchronism in the entire region composed of these service areas in conjunction with minimum costs, a respective highly stable frequency standard is provided in each of the local exchanges. Synchronization between the local exchanges and a main exchange may take place daily, weekly, or monthly. The main exchange supplies modulation signals to the local exchanges. <IMAGE> |
