Audible alarm unit

Details Audible alarm unit Audible alarm unit

1977-04-14

1979-02-13

Pitts, Harold I.

Communications: electrical

Audible indication

Ultrasonic pest control

340384R, 331116R, H03B 530, G08B 300

Patent

active

041398424

ABSTRACT:
The present invention is an audible alarm unit including a coil, a resistor, an NPN transistor, and a piezoelectric transducer having first and second electrodes and a feedback electrode. The collector and emitter of the transistor and the coil are connected in series between positive and negative terminals of a direct current power source. The base of the transistor is connected to the collector through the resistor. The first and second electrodes of the piezoelectric transducer are connected either to both ends of the coil or to the collector and emitter of the transistor, respectively. The feedback electrode of the piezoelectric transducer is connected to the base of the transistor.

REFERENCES:
patent: 3728641 (1973-04-01), Fujita
patent: 3778648 (1973-12-01), Kawada
patent: 3878408 (1975-04-01), Nemoto
patent: 3878481 (1975-04-01), Healey
patent: 4001724 (1977-01-01), Keller

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