PROTECTION OF SUBSCRIBER LINE INTERFACE CIRCUITS (SLICS) WITHOUT DEGRADATION IN LONGITUDINAL BALANCE

A subscriber line interface circuit has first and second line drivers for connection to respective tip and ring lines of a subscriber loop. Each of said line drivers is in a feedback loop. A current limiting device is included in each feedback loop for providing protection against excessive current. In this way the effective impedance of the current limiting devices is small relative to their actual impedance and as a result any impedance mismatch between the current limitin g devices has a negligible effect on the longitudinal balance of the subscribe r loop.