Ultrasonic alarm system

Details Ultrasonic alarm system Ultrasonic alarm system

1974-02-04

1976-03-02

Habecker, Thomas B.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340 15, 340287, 340301, 340312, 200 6174, G08B 108, H04B 1100

Patent

active

039421767

ABSTRACT:
An ultrasonic alarm system comprising a transmitter having an oscillator which produces an ultrasonic carrier frequency signal. An audio signal generator produces a signal which modulates the carrier signal. The modulated signal is applied to a crystal through a tuned circuit. The transmitter is energized by operating a pushbutton which remains latched in operative position and which is unlatched only by the use of special devices. A plurality of receivers are provided and individual receivers are positioned at different locations throughout the premises to be protected. Each receiver includes a demodulator that demodulates the received signal and applies the same to a phase locked loop type phase detector which actuates an alarm when the demodulated signal is present. The alarm indicates the particular receiver that has been activated so that help may be dispatched immediately to the correct location.

REFERENCES:
patent: 2766358 (1956-10-01), Davidson
patent: 3376506 (1968-04-01), Sontag
patent: 3418650 (1968-12-01), Rich et al.
patent: 3440635 (1964-04-01), Hull
patent: 3478344 (1969-11-01), Schwitzgebel et al.
patent: 3696384 (1972-10-01), Lester

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