Importance

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Abstract

Integrated Services Digital Network (ISDN) terminal equipments (TEs) are remotely powered from a central source via line interface circuits. One function of the line interface circuit is that of conducting energizing direct current for the associated telecommunications terminal equipment while providing effective overcurrent protection in spite of widely variable load current requirements which occasionally may mimic a faulty over current condition. The line interface circuit includes first and second power terminals for connection to a source of power, first and second line terminals for supplying said energizing direct current, and a current control means, being connected between a one of the first and second power terminals and a respective one of the first and second line terminals, for temporarily switching off an inrush current in excess of a dynamic limit, and permanently switching off a load current in excess of a static limit until a virtual open circuit condition occurs across the first and second line terminals.

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First Claim