| 摘要 |
An alarm system is disclosed comprising a control panel (1), a first plurality of detectors (4) and a second plurality of sounders (5) mounted upon a common pair of wires. The system is operated by a method comprising the generation by one or more detectors of an alarm signal; the generation of a predetermined power pulse pattern at the control panel at a level sufficient to power the sounders; recognition of the pulse pattern at the alarm indicating devices and generation of alarm indication in response thereto.
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