Telephonic communications – Supervisory or control line signaling – Substation originated
Patent
1986-02-05
1988-02-02
Dwyer, James L.
Telephonic communications
Supervisory or control line signaling
Substation originated
379375, H04M 126
Patent
active
047232757
ABSTRACT:
A subscriber telephone set which comprises a multifrequency dialing tone oscillator, a microprocessor connected thereto for controlling selection of the tones produced thereby, and an acoustic signal element for producing a ringing sound corresponding to ringing tones applied thereto. The microprocessor prevents incorrect triggering of the acoustic signal element by noise voltages on the subscriber line by verifying that the amplitude of the ringing current received on the line exceeds a predetermined level, and also that the ringing current frequency corresponds to the frequency of a resetting signal internally generated within the microprocessor. Upon such verification, the microprocessor controls the dialing tone oscillator to generate a ringing tone which is applied to the acoustic signal element to cause it to generate a ringing sound, the dialing tone oscillator thereby also serving as a ringing tone generator for activating the acoustic signal element.
REFERENCES:
patent: 4491691 (1985-01-01), Embree et al.
patent: 4571462 (1986-02-01), Janssen
All Telephone Functions in One Chip PBL3780, Bengt Berg, #No. 3, 1985, Ericsson Review.
LSI for Telecommunications, David W. Pace, Apr. 1984, Telecommunications North American Edition.
Frerichs Werner
Grucza Hubert
Hirth Peter
Briody Thomas A.
Dwyer James L.
Oisher Jack
Streeter William J.
U.S. Philips Corporation
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