Browse Prior Art Database

Constant Voltage Resistive Feeder for Telephone Line Interface Circuits

IP.com Disclosure Number: IPCOM000045650D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Ballatore, D: AUTHOR

Abstract

This article describes an improvement to the feeder used to supply a telephone line with a DC current. The improved feeder behaves as a constant voltage source as long as the output current is below a current reference, and as a linear resistive feeder when the output current is above the current reference.

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Constant Voltage Resistive Feeder for Telephone Line Interface Circuits

This article describes an improvement to the feeder used to supply a telephone line with a DC current. The improved feeder behaves as a constant voltage source as long as the output current is below a current reference, and as a linear resistive feeder when the output current is above the current reference.

Referring to Fig. 1, the feeder comprises a low-pass filter including inductor L and capacitor C, and having its input connected to a battery voltage source E through switching transistor T1. Diode D is a free-wheeling diode when T1 is off. The operation of transistor T1 is controlled by the output from comparator COMP through transistor T2. Comparator COMP compares the voltage drop across resistor R to the raised sawtooth voltage Vs, illustrated in Fig. 2.

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