SUBAUDIBLE FREQUENCY DETECTION SYSTEM

Disclosed are systems usable in detecting subaudible frequencies. In one embodiment a seismic detector is shown positioned in the earth and responding to the subaudible frequency vibrations caused by a moving person. A subaudible frequency signal is developed in response to the detected vibrations a...

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Bibliographic Details
Main Author PAUL S. DENNIS JR
Format Patent
LanguageEnglish
Published 09.05.1972
Subjects
ALARM SYSTEMS
DETECTING MASSES OR OBJECTS
GEOPHYSICS
GRAVITATIONAL MEASUREMENTS
MEASURING
ORDER TELEGRAPHS
PHYSICS
SIGNALLING
SIGNALLING OR CALLING SYSTEMS
TESTING
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