Telephone tone detector

Details Telephone tone detector Telephone tone detector

1988-08-09

1989-09-19

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Signal receiver

379283, 34082548, 34082574, H04Q 912

Patent

active

048688720

ABSTRACT:
A tone detector comprising a circuit for detecting multi-frequency dialing (DTMF) signals applied to an input terminal and for generating a "DTMF present" indicating signal, and a circuit for detecting the presence of supervisory signals applied to the input terminal and for generating a "supervisory signal present" indicating signal. The dialing tones are converted to digital value signals and are preferably stored in a shift register. The digital value signals and the supervisory signals are applied in serial form to an output terminal. The "DTMF present" indicating signal is applied to a "DTMF present" terminal. Accordingly the presence of the "DTMF present" indicating signal can be monitored and thereby indicate whether the signal present on the output terminal is a digital value signal or a supervisory tone present indicating signal. The invention is thus realizable in a significantly reduced pin count integrated circuit chip for use in domestic controlling apparatus to be connected to telephone lines, such as telephone answering machines, utility meter readers, security devices, etc.

REFERENCES:
patent: 4521647 (1985-06-01), Olson et al.
patent: 4696031 (1987-09-01), Freudberg et al.

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