Telephonic communications – Centralized switching system – Power supply
Patent
1984-04-30
1987-11-10
Rubinson, Gene Z.
Telephonic communications
Centralized switching system
Power supply
379398, 379413, 333 17R, 333213, 330104, H04M 1900
Patent
active
047062819
ABSTRACT:
Battery feed circuits function to supply a predetermined current to the communication pair and include circuitry to counteract the effects of balanced longitudinal signals which appear on the communication pair. Prior art battery feed circuits use either expensive matched power resistors or matched and tracking current sources to provide both the dc current and the necessary balance. The subject battery feed circuit separates the two functions: a pair of poorly matched inexpensive power resistors provide the basic dc current; and associated pair of low power electronic circuits supply compensation signals to provide the necessary balance. The compensation signals are applied to the power resistors in a manner to obtain precision resistor (.+-.0.1%) characteristics from the inexpensive (.+-.5%) power resistors.
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"A High-Voltage IC for a Transformerless Trunk and Subscriber Line Interface", Denis W. Aull et al., IEEE Journal of Solid-State Circuits, vol. SC-16, No. 4, Aug. 1981, pp. 261-266.
American Telephone and Telegraph Company
AT&T Information Systems Inc.
Graziano James M.
Rubinson Gene Z.
Vaas R.
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