| 摘要 |
<p>Each piece of monitoring equipment (10) contains a transmitter (S), a receiver (E), a detector (12) and an alarm device (15). So that the receiver does not have to be switched on continuously, in order to listen to a transmitter signal from another piece of monitoring equipment, the receiver is activated at time intervals, in which it scans over short periods for the existence of a transmitter signal. If the detector triggers, the transmitter signal runs for a span of time.</p> |
