Abstract: An intrusion detector operating mode selection circuit sets an intrusion detector operating mode responsive to an encoded acoustic signal. An acoustic signal decoder receives an encoded acoustic signal and generates a mode selection signal in response thereto. The encoded acoustic signal is a plurality of spaced-apart acoustic pulses encoded by the relative inter-pulse timing of the spaced-apart pulses. A mode of the intrusion detector is set responsive to the mode selection signal.

Abstract: Dual microphones and a time-of-arrival processing circuit comprise a direction-sensing system which improves the false alarm immunity of an acoustic glass break detector by restricting its coverage to a well-defined zone. By comparing the arrival times of an abrupt sound at two spaced microphones, the processing circuit determines the direction of the sound. If the sound originated in the intended coverage zone, the processing circuit generates a signal which enables the glass break detector; otherwise, the detector is inhibited. When the improved glass break detector is oriented so that potential false alarm sources are outside the coverage zone, false alarm immunity is enhanced.

Abstract: A vehicle detector is disclosed wherein either a glass breakage signal or a door opening signal causes an alarm. The glass breakage signal is caused by the detection of high audio frequency simultaneously accompanied by the detection of a positive pressure change. The door opening signal is generated by the detection of a negative pressure change, which is not preceded by a positive pressure change.

Abstract: A supervisory circuit for use with an audio intrusion detection system is disclosed. The supervisory circuit periodically generates an audio test signal which is supplied to a sounder which emits an audio test sound. The audio test sound is directed into a volume of space, in the same volume of space as which the audio intrusion detection system is directed to detect. The audio intrusion detection system detects the test sound and generates an audio test signal in response thereto. During the generation of the audio test sound, the comparing apparatus of the audio intrusion detection system is disabled. The audio test signal generated by the audio intrusion detection system is then compared to a test threshold signal. A test result signal is generated in response to the comparison with the test result signal indicative of the operability of the audio intrusion detection system.