| 摘要 |
In an alarm system a central signal station periodically transmits interrogation signals, preferably in the form of infrared radiation packets to remotely located detectors which transmit a response signal back to the central signal station after differing time delays that are characteristic for the individual detectors and which permit the localization of the source of the response signal. In an alarm state, the detectors respond to every interrogation signal, in the normal operational state to only every mth interrogation signal, i.e. less often, and in a state of diminishing battery potential to only every small pth interrogation signal, i.e. even less often. The state of the individual detectors is determined from the frequency with which the response signals are transmitted back by the detectors, that is the ratio of the response signals to the interrogation signals.
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