| 摘要 |
<p>A transmitter transmits a control signal (32) and a message (30) on the same voice/data channel to at least one receiver (12). Control signal (32) comprises code words (40, 44) to designate which receiver (12) is not to have the volume reduced to zero. The control signal (32) also controls the magnitude of the volume of the recovered or received message (30) and is non-audible so that it is not heard by the person listening to the message (30). The time duration of a control signal (54) determines the time that the message (30) will be at the controlled volume magnitude.</p> |
