Telephone tone detector

Details Telephone tone detector Telephone tone detector

H - Electricity

04

Q

379/20

H04Q 1/457 (2006.01) H04M 1/50 (2006.01) H04Q 1/444 (2006.01) H04Q 1/453 (2006.01)

Patent

CA 1268570

ABSTRACT OF THE DISCLOSURE A tone detector comprising means for detecting multi-frequency dialing (DTMF) signals applied to an input terminal and for generating a "DTMF present" indicating signal, and means 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.

544585

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