Subscriber line interface circuit having means for combining dc and ac feedback signals

Abstract From the Canadian patent

Subscriber Line Interface Circuit Having Means for Combining DC and AC Feedback Signals" ABSTRACT OF THE DISCLOSURE, A subscriber line interface circuit comprises a balanced amplifier having positive and negative inputs for amplifying a voltage thereacoss to generate a pair of mutually complementary voltages across true and complementary outputs. Four resistors of a first value are respectively connected between a subscriber tip line and the negative input, between a subscriber ring line and the positive input, between the negative input and true output and between the positive input and complementary output. Two resistors of a second value smaller than the impedance of the subscriber loop …