The MC33120 is designed to provide the interface between the 4-wire side of a central office, or PBX, and the 2-wire subscriber line. Interface functions include battery, feed, proper loop termination AC impedance, hookswitch detection, adjustable transmit, receive, and transhybrid gains, and single/double fault indication. Additionally the MC33120 provides a minimum of 58dB of longitudinal balance (4-wire and 2-wire).
The transmit and receive signals are referenced to analog ground, while digital signals are referenced to digital ground, easing the interface to codecs, filters, etc. The 2 status outputs (hookswitch and faults) and the Power Down Input are TTL/CMOS compatible. The Power Down Input permits local shutdown of the circuit.
Internal drivers allow the external loop current pass transitors to be standard bipolar transistors (non-Darlington).
The MC33120 is available in a 20 pin DIP and a 28 pin PLCCC surface mount package.
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