Circuit for supplying direct current to telephone station sets

Details Circuit for supplying direct current to telephone station sets Circuit for supplying direct current to telephone station sets

1977-05-25

1978-05-02

Robinson, Thomas A.

179 18FA, H04M 1908

Patent

active

040876470

ABSTRACT:
A local battery feed circuit for telephone station sets comprises two half circuit portions substantially symmetric about an imaginary line midway between the TIP and RING telephone lines. Each half circuit includes a current drive amplifier including a pair of up-down emitter follower transistors and a driver transistor. A coupling capacitor and matched resistors provide common mode interference reduction without degrading differential mode signals. Power supply noise is substantially eliminated by transistors in each half circuit arranged to produce an a.c. current equal and opposite to that generated from the power source.

REFERENCES:
patent: 3649769 (1972-03-01), Pest
patent: 3940572 (1976-02-01), Burgess
patent: 3955052 (1976-05-01), Orbach
patent: 4007335 (1977-02-01), Hetherington et al.

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