Alarm system testing circuit

摘要

A testing circuit for an alarm system is disclosed. The testing circuit is operable in an alarm system that includes a microphone for receiving an audio sound and a detector/generator for detecting audio characteristics in the audio sound corresponding to breaking glass and for generating an alarm signal in response thereto. The audio characteristics corresponding to breaking glass include first and second frequency components in timed relation, wherein the first frequency must be detected prior to the second frequency for an alarm to be generated. The testing circuit includes a trigger circuit for receiving the audio signal and for detecting the first-frequency component thereof, the trigger circuit activating the detector/generator in response to detection of the first-frequency component; a test circuit for periodically generating a test audio sound at the second frequency, the trigger circuit remaining operable to detect the first-frequency component during generation of the test audio sound; and circuitry operable during generation of the test audio sound for detecting the test audio sound and for (a) resetting the test circuit in response to detection of the test audio sound and (b) generating a fault signal upon non-detection of the test audio sound. The glass-break sensor is not disabled during a self-test and utilizes a test sound at a frequency that is normally used by the sensor for detecting breaking glass.