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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Main Author | |
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Format | Patent |
Language | English |
Published |
09.05.1972
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Subjects | |
Online Access | Get full text |
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Summary: | 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 and is translated by modulating and mixer circuitry into an output signal in which each frequency component in the subaudible frequency signal is represented by a single corresponding audio frequency component. The output signal is supplied to a loudspeaker for aurally distinguishing the representative audio frequency components to detect the person. Other embodiments are also covered. |
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Bibliography: | Application Number: USD3662326 |