Arrangement for detecting the breaking of window glass

摘要

Detector 10 in the form of a piezoelectric element or accelerometer is disposed on a window pane or its frame and provides a signal, on physically sensing breakage of the pane, to AND gate 12. Microphone 13 faces the pane and provides a signal on audibly detecting breakage of the pane, to the AND gate 12, which provides an alarm output only when both signals are received substantially simultaneously, thereby avoiding spurious alarms.