ULTRASONIC INTRUSION DETECTION SYSTEM SIGNAL PROCESSING CIRCUIT

摘要

An electronic device for processing the amplitude modulations of a received ultrasonic carrier wave to produce an alarm signal when the pattern of the amplitude modulations is characteristic of an alarm condition. The device produces an electrical signal which is representative of the amplitude modulations of a received wave. When the electrical signal has a frequency within a predetermined pass-band, is of at least a predetermined amplitude, and persists for a minimum time interval, an alarm signal is produced.