| 摘要 |
A security system having one or more sending units for transmitting an electromagnetic signal representative of a condition such as fire, smoke, intrusion, battery condition, an emergency or other condition to a central receiving unit. Upon reception of an electromagnetic signal, the receiving unit provides an electromagnetic carrier detect signal to a microprocessor. A software timer within the microprocessor keeps track of the time over which the carrier is detected. If the carrier detection continues for a time longer than about 20 seconds, then a jamming indication signal is provided to one or more outputs. While the system is being jammed, alarms are ignored thus avoiding false alarms due to interference.
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