Method and apparatus for minimizing system oscillations caused b

Details Method and apparatus for minimizing system oscillations caused b Method and apparatus for minimizing system oscillations caused b

1998-02-26

1999-12-07

Kuntz, Curtis A.

Telephonic communications

Telephone line or system combined with diverse electrical...

Having transmission of a digital message signal over a...

379 9326, 375222, H04M 1100

Patent

active

059995971

ABSTRACT:
An apparatus and method for canceling system oscillations caused by acoustical coupling is provided. The invention can be implemented in a low voltage environment and as an integrated circuit. Audio voltage signals generated by a microphone are provided as input to a data/fax/voice modem. The data/fax/voice modem processes the audio voltage signals and outputs differential transmit voltage signals to a hybrid/daa circuit for converting to a two-wire (tip and ring) circuit before connecting to a communication device such as a land based telephone or a cellular radio. Audio voltage signals generated by the communication device are provided via a two-wire (tip and ring) circuit to the hybrid/daa circuit for converting into a four-wire circuit and then provided as input to the data/fax/voice modem as differential receive voltage signals. The differential transmit voltage signals are amplified and phase shifted so that they are out of phase relative to the differential receive voltage signals which are also amplified. The differential transmit voltage signals and the differential receive voltage signals are then added together. The combined signals are then output to an audio speaker.

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patent: 5636323 (1997-06-01), Uemeoto et al.
patent: 5771278 (1998-06-01), Brown

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