Intrusion detector sensitive to resonant frequency of breaking g

Details Intrusion detector sensitive to resonant frequency of breaking g Intrusion detector sensitive to resonant frequency of breaking g

1975-06-16

1976-08-03

Scott, James R.

Electricity: circuit makers and breakers

Special application

Anti-intrusion type

200235, 340274R, H01H 302, H01H 2904, G08B 1308

Patent

active

039730956

ABSTRACT:
An intrusion detector which senses the motion and vibration caused by intrusion comprises a base plate secured to the surface to be protected, and a housing coaxially and rotatably joined to the base plate. Within the housing is disposed a mercury switch parallel to the protected surface. The mercury switch comprises a tubular envelope housing a drop of mercury and a pair of electrodes. The electrodes are of disparate lengths so that the mercury must travel to one extreme end of the tube to complete the circuit. Rotation of the housing alters the orientation of the switch envelope with respect to horizontal, permitting the device to be employed as a normally-open or normally-closed motion switch. Further, the switch is sensitive to motion colinear with the axis of the envelope, so that, by rotation of the housing, its sensitivity may be finely adjusted to stimuli ranging between loud noises to broachment of the protected surface. In one embodiment the electrode structure of the switch is designed to sense the particular frequency of breaking glass, and to close when such frequency is present.

REFERENCES:
patent: 3706090 (1972-12-01), Callaghan
patent: 3899784 (1975-08-01), McHenry

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