Alarm system for detecting disturbance of a solid medium

摘要

A window pane or other acoustically propagative medium is excited with a source of sonic or ultrasonic energy by use of a suitable transducer affixed to the pane and the amplitude and/or phase of the resulting pattern is sensed and processed to derive a signal repesentative thereof. Violation of the integrity of the pane such as by cutting or breakage thereof or disturbance of the pane such as touching or leaning on the pane causes a sensible change in the pattern and from which is derived an output signal for signifying an alarm condition when the change exceeds a predetermined threshold level.