Telephonic communications – Subscriber line or transmission line interface – Hybrid circuit
Patent
1991-03-27
1992-12-29
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Hybrid circuit
379345, 379403, 370 32, 333119, H04B 320
Patent
active
051757630
ABSTRACT:
A communication system has a two-wire communications path carrying analog transmission and reception signals, and a four-wire communications path including a two-wire transmission path carrying digital transmission signals and a two-wire reception path carrying digital reception signals. A two-wire/four-wire converter for coupling the two-wire communications path to the four-wire communications path includes an analog/digital converter having an input coupled to the two-wire communications path and an output. A digital filter has an adjustable communications function for generating a predetermined terminating impedance for the two-wire transmission path. The digital filter has an input connected to the output of the analog/digital converter and an output connected to the two-wire reception path. An adder has one input connected to the two-wire reception path, another input connected to the two-wire transmission path and an output. A subtractor has one input connected to the output of the adder, another input coupled to the output of the analog/digital converter and an output. A digital/analog converter has an input coupled to the output of the substractor and an output coupled to the two-wire communications path. A resistor is connected in parallel with the input of the analog/digital converter.
REFERENCES:
patent: 4161633 (1979-07-01), Treiber
patent: 4178569 (1979-12-01), Reutter et al.
patent: 4351060 (1982-09-01), Treiber
patent: 4381561 (1983-04-01), Treiber
patent: 4652703 (1987-03-01), Lu et al.
patent: 4757527 (1988-07-01), Beniston et al.
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Siemens Forschungs- und Entwicklungsberichte, vl. 5, No. 5, 1986, pp. 253-258; Vogel et al.; "A Signal-Processing Dodec Filter for PCM Applications"; p. 254, left column, line 33.
Dwyer James L.
Greenburg Laurence A.
Lerner Herbert L.
Shehata M.
Siemens Aktiengesellschaft
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