Tone discrimination circuit

Details Tone discrimination circuit Tone discrimination circuit

1983-10-14

1985-05-28

Isen, Forester W.

Electrical audio signal processing systems and devices

Monitoring of sound

381 58, 340540, 73646, 179 5R, G08B 1700, H04R 2900

Patent

active

045205035

ABSTRACT:
A tone discrimination circuit for use with audible smoke or fire detectors or similar audible devices, which automatically emits an output electronic alarm signal, for notification of persons at remote locations, upon input of a proper audio tone from the smoke detector or other audible device. The circuit contains in series a microphone, a two stage audio amplifier, a frequency detector, and a time discrimination circuit. The circuit emits an output electronic alarm signal if and only if the audio input signal has sufficient amplitude, the desired frequency, and the desired duration. In the preferred embodiment the duration must be 20 seconds or longer, though the circuit allows the audio input to cease for a period less than 0.25 seconds, without loss of the output signal. The timing periods are adjustable.

REFERENCES:
patent: 3492426 (1970-01-01), Foreman et al.
patent: 3647974 (1972-03-01), Geisler et al.
patent: 3713127 (1973-01-01), Keledy et al.
patent: 4091366 (1978-05-01), Lavallee
patent: 4346374 (1982-08-01), Groff

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