Alarm system responsive to intrusion induced phase unbalance

Details Alarm system responsive to intrusion induced phase unbalance Alarm system responsive to intrusion induced phase unbalance

1987-08-19

1989-02-21

Swann, III, Glen R.

Communications, electrical: acoustic wave systems and devices

Echo systems

Presence or movement only detection

340538, 367 94, G08B 1316, G08B 108

Patent

active

048072559

ABSTRACT:
An alarm system includes apparatus to be placed in a room to transmit ultrasonic wave signals that rebound off the room's walls and contents, to, and receive the rebounding signals, and to phase balance the transmitted and received signals in order to detect a subsequently unbalance condition caused by a changed in the rebounding signals due to intrusion activity, which produces an electrical alarm signal. Other circuitry responds to reception of an alarm signal to produce an audible or visible alarm. The alarm signal is typically transmitted over electrical power lines.

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