Importance

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Abstract

A self-contained pre-intrusion detection and alarm system for doors and other closures, the system including an rf oscillator circuit incorporating a tank circuit which includes an antenna. The system also includes a detection and processing circuit effective to detect and amplify a change in the voltage in the rf oscillator circuit caused by a change in the antenna to ground capacitance; an audio oscillator circuit; time delay circuitry connected between the detecting and processing circuit and the audio oscillator circuit and controlling the energization of the audio oscillator circuit; and an alarm electrically connected to and controlled by the audio oscillator circuit for alerting occupants of potential danger of intrusion and also deterring potential intruders from continuing their activities toward intrusion.

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First Claim