| 摘要 |
<p>A communication apparatus comprises a network of transmitters and receivers communicating with each other by means of UHF radio frequency signals. Each transmitter is linked to one or more associated receivers and can be individually activated to transmit a selected one of a number of different predetermined messages to its associate receivers along a corresponding communication channel. Each transmitter is activatable by means of a respective message selector which enables a user thereof to select the predetermined message to be transmitted by the transmitter.</p> |
