| 摘要 |
<p>An alarm apparatus using a single pair of signal wires (20) coupled to detector units (30) and alarm output units (40). Voltage on the signal wires (20) is reversed to indicate an alarm condition and periodically dipped to a third voltage level to decouple the alarm output units (40) enabling the detector units (30) to be monitored in the alarm state. <IMAGE></p> |
