| 摘要 |
<p>A radio communication system having a plurality of transmitters (10, 20, 30 & 40) which each transmit on a different channel and which each include means (11, 12) for periodically transmitting a channel signal on the transmitter's channel, and a receiver (50) including a tuner (54) for tuning the receiver to any one of the channels, a scanner (64) for causing the tuner to scan the channels and a re-settable timer (62) for activating the scanner when a channel signal has not been received on the channel to which the receiver is tuned for a predetermined time which is greater than the time period of the channel signals and for de-activating the scanner when a channel signal is received on the channel to which the receiver is tuned. The channel signals may be unmodulated carrier signals and the system may operate as a two-way duplex system. The system allows a mobile receiver to be automatically tuned to a correct channel when moving between different channel coverage areas without the transmitters continuously transmitting unmodulated carrier signals.</p> |
