Alarm signal processing means

An intruder detector system such as a microwave fence having a transmitter 10 and receiver 12 produces a signal proportional to the disturbance created by an intruder. The signal is processed by a microwave detector 14 and processor 16 and supplied, as DC voltage output to two channels 18, 20. First...

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Bibliographic Details
Main Author ROGER WILLIAM LESLIE HOYLE
Format Patent
LanguageEnglish
Published 19.09.1990
Subjects
ALARM SYSTEMS
ORDER TELEGRAPHS
PHYSICS
SIGNALLING
SIGNALLING OR CALLING SYSTEMS
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Summary:An intruder detector system such as a microwave fence having a transmitter 10 and receiver 12 produces a signal proportional to the disturbance created by an intruder. The signal is processed by a microwave detector 14 and processor 16 and supplied, as DC voltage output to two channels 18, 20. First channel 18 compares the DC voltage strength to a pre-set value stored in a first threshold detector/comparator 22. On the DC voltage exceeding the pre-set value an alarm relay 24 is actuated causing actuation of an alarm (not shown). Second channel 20 passes the voltage through a first filter 26 which removes high frequency signal variations characteristic of a fast moving intruder. Thus the signal which is compared with a second pre-set value stored in a second threshold detector/comparator 28 relates only to slow moving intruders and the pre-set value can therefore be set for a lower level of disturbance as would be caused by a crawling human intruder. The intruder detection system may alternatively be a parallel wire electric field sensor.
Bibliography:Application Number: GB19890005802