Communications – electrical: acoustic wave systems and devices – Distance or direction finding
Patent
1991-12-10
1993-03-16
Eldred, J. Woodrow
Communications, electrical: acoustic wave systems and devices
Distance or direction finding
367131, 367136, 367153, 367157, 310337, 340566, G01S 380
Patent
active
051950600
ABSTRACT:
An apparatus for detecting a person in a body of water includes a transmitter for generating an electrical swept frequency signal having a frequency that continuously varies between upper and lower limits, at least one pair of transducers disposed in a body of water including a transmitting transducer connected to receive the swept frequency signal for launching a beam of acoustical waves in response to the swept frequency signal in the body of water and a receiving transducer disposed opposite the transmitting transducer for receiving the acoustical waves and for converting received acoustical waves into an electrical received signal, and a receiver connected to the receiving transducer for producing a detected signal in response to the received signal, for producing a threshold signal in response to the detected signal, and for initiating an alarm when the detected signal falls below the threshold for at least a predetermined length of time.
REFERENCES:
patent: 2783459 (1957-02-01), Lienau et al.
patent: 4747085 (1988-05-01), Dunegan et al.
patent: 4932009 (1990-05-01), Lynch
Eldred J. Woodrow
Marcorp Inc.
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