Patent
1982-12-01
1985-12-10
Brown, Thomas W.
179170R, H04B 158
Patent
active
045581851
ABSTRACT:
For the purpose of realizing a line circuit, especially a two-wire four-wire conversion circuit of a telephone exchange in the form of LSI and providing the conversion circuit with an impedance which is suitable to a side tone characteristic of the telephone set, in a line circuit composed of a hybrid circuit wherein the four-wire input line is connected to the two-wire subscriber line via a buffer amplifier and a terminating impedance and in addition the four-wire output line is connected to the output of a subtractor which subtracts an input signal of the four-wire input line passed through a filter circuit from a signal fed from the two-wire subscriber line, the terminating impedance is formed by a resistor component and in addition a feedback circuit having such a transfer characteristic that the impedance of the line circuit seen from the two-wire subscriber line side will become a specified complex impedance is installed between a line which couples the two-wire subscriber line to the subtractor and an input of the buffer amplifier.
REFERENCES:
patent: 4100515 (1977-05-01), Gupta
patent: 4174470 (1979-11-01), Seidel
patent: 4284859 (1981-08-01), Araseki
patent: 4358643 (1982-11-01), Levy
patent: 4387273 (1983-06-01), Chea, Jr.
patent: 4388500 (1983-06-01), Regan
"An Electric Hybrid with Adaptive Balance", B. Dotter et al., International Conf. on Communications, Seattle, Wash., Jun. 1980, pp. 44.5/1-5.
"Hybrid with Automatic Selection of Balance Networks", Alejandro de la Plaza, IEEE Int'l. Symposium on Circuits and Systems, Chicago, Ill., Apr. 1981, pp. 27-29.
"An Electronic Hybrid with Adaptive Balancing for Telephony", D. Messerschmitt, IEEE Transactions on Communications, Aug. 1980, vol. COM 28, No. 8, pp. 1399-1407.
Amada Eiichi
Morikawa Yuichi
Saito Kazuo
Shirasu Hirotoshi
Brown Thomas W.
Hitachi , Ltd.
Nippon Telegraph & Telephone Public Corp.
Vaas R.
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