Signal detection circuit and telephone apparatus

Details Signal detection circuit and telephone apparatus Signal detection circuit and telephone apparatus

1997-02-20

1999-01-19

Tsang, Fan S.

Telephonic communications

Special services

Call waiting

379 9335, 379163, 379283, 379386, H04M 342

Patent

active

058622101

ABSTRACT:
A signal detection circuit includes band pass filters for detecting frequency components of a Call Alert signal (CAS) signal, a tone detection circuit for detecting whether or not a signal component is present in the output signals of the band pass filters, and two types of guard time setting circuits that have different guard times. When the CAS signal component is present, a transmitting speech signal is muted. Thereafter, with the guard time setting circuit having the normal guard time, it is determined whether or not the signal component lasts for a predetermined time period. Since the CAS signal is detected with two types of guard times, even if the transmitting speech signal contains a frequency component of the CAS signal, the transmitting speech signal is not mis-detected as the CAS signal.

REFERENCES:
patent: 5263084 (1993-11-01), Chaput et al.
patent: 5519774 (1996-05-01), Battista et al.
patent: 5649002 (1997-07-01), Brady et al.

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