NCJ Number
26209
Journal
SECURITY GAZETTE Volume: 16 Issue: 11 Dated: (NOVEMBER 1974) Pages: 404-405,AND 407
Date Published
1974
Length
3 pages
Annotation
THE OPERATING PRINCIPLES OF ULTRASONIC MOVEMENT DETECTORS ARE DISCUSSED ALONG WITH POSSIBLE SOURCES OF FALSE ALARMS AND TECHNOLOGICAL ADVANCES THAT PERMIT DETECTORS TO IGNORE UNWANTED SIGNALS.
Abstract
THESE DEVICES RELY ON THE DOPPLER EFFECT WHICH ACCOUNTS FOR INCREASES OR DECREASES IN REFLECTED WAVE FREQUENCY DEPENDING ON WHETHER THE INTRUDING OBJECT IS APPROACHING OR RETREATING FROM THE DETECTOR.