Active impedance line feed circuit

Details Active impedance line feed circuit Active impedance line feed circuit

1982-06-10

1985-04-30

Rubinson, Gene Z.

179 16AA, 179 18FA, 179 70, 179170NC, H04M 174, H04M 176, H04M 1900

Patent

active

045145954

ABSTRACT:
A line circuit includes tip and ring voltage amplifiers each having an output resistively connected via tip and ring feed resistors to tip and ring leads in a telephone line. The tip and ring feed resistors have closely matched ohmic values, and are part of a resistance network which also includes first and second voltage dividers. The first voltage divider is connected in series between the output of the tip voltage amplifier and an end of the ring feed resistor remote from the output of the ring voltage amplifier, and includes a first voltage tap. The second voltage divider is connected in series between the output of the ring voltage amplifier and an end of the tip feed resistor remote from the output of the tip voltage amplifier, and includes a second voltage tap. A control circuit includes a differential input connected across the first and second voltage taps. In operation the control circuit causes the tip and ring voltage amplifiers to provide energizing direct current for the telephone line. Tip and ring feedback networks, connected across the respective tip and ring feed resistors, provide feedback signals to the tip and ring voltage amplifiers such that in operation common mode rejection of longitudinally induced a.c. signals on the telephone line is enhanced.

REFERENCES:
patent: 3748395 (1973-07-01), Herter
patent: 4319093 (1982-03-01), Bars
patent: 4331842 (1982-05-01), Kiko
patent: 4387273 (1983-06-01), Chea, Jr.
patent: 4388500 (1983-06-01), Regan
patent: 4431868 (1984-02-01), Bolus et al.
patent: 4476350 (1984-10-01), Aull et al.
patent: 4484032 (1984-11-01), Rosenbaum
patent: 4485277 (1984-11-01), Minch et al.
"Balanced Electronic Hybrid Circuits", D. E. Fisk et al., IBM Technical Disclosure Bulletin, Jul. 1973, vol. 16, No. 2, pp. 495-496.
"A High-Voltage for a Transformerless Trunk and Subscriber Line Interface", by D. W. Aull et al., IEEE Journal of Solid-State Circuits, vol. SC-16, No. 4, Aug. 1981, pp. 261-266.

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