Donald M Cross

US Patent:

48642886, Sep 5, 1989

Filed:

Dec 18, 1987

Appl. No.:

7/134965

Inventors:

Donald R. Cross - Torrance CA

Assignee:

Iwata Electric Co., Ltd. - Tokyo

International Classification:

G08B 1322

US Classification:

340669

Abstract:

A Hall-effect device and a magnet are mounted on respective resonant bridge supports in magnetic field relationship whereby movement of either the magnet or the Hall-effect device produces a change in the field strength at the Hall-effect device. The two support structures with their mounted components exhibit different natural resonant frequencies whereby stimuli in either of two different ranges causes one or both of the magnet or Hall-effect device to move at their resonant frequency producing a signal. Signal processing circuitry disregards D. C. signals from the Hall-effect device and responds only to A. C. signals, indicative of shocks in the 1000 to 2000 Hertz range or movement of the detector with components in less than the 150 Hertz range. Three different bridge structures are disclosed, one with separate bridges, one employing common support columns and one which is integrally molded.