Subscriber line interface circuitry includes an integrated circuit having
sense inputs for a sensed tip signal and a sensed ring signal of a
subscriber loop. The integrated circuit generates a subscriber loop
linefeed driver control signal in response to the sensed signals. In one
embodiment, A linefeed driver includes power circuitry for providing
battery feed to the ring and tip nodes of the subscriber loop in
accordance with the linefeed control signal. The linefeed driver includes
sense circuitry providing a sensed tip signal and a sensed ring signal.
The sensed tip and ring signals correspond to a tip current and a ring
current of the subscriber loop. In one embodiment, the integrated circuit
is a complementary metal oxide semiconductor (CMOS) integrated circuit.
In one embodiment, the linefeed driver comprises only discrete
components.