| 摘要 |
A detector and indicator for burglar alarms is provided wherein passive resonators, each tuned to a different frequency, are employed across each of the normally closed series switches of the burglar alarm. An alternating current generator is connected to the series line and tuned progressively to the frequency of each of the passive resonators. If an open circuit occurs across any of the resonators, a detector circuit detects the high impedance which results and actuates an indicator circuit wherein the indicator is selected for the frequency of the resonator of a particular location. Even if a plurality of switches are open, the selection circuit will be activated for the particular locations of the open switches.
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