Transceiver unit for a telecommunication system

Abstract

A transceiver for use with a digital telephone apparatus adapted to be connected for duplex communication to a telephone speech transmission line includes a receiving unit and a transmitting unit. The receiving unit processes an incoming serial ternary level signal stream composed of alternate mark inverted (AMI) encoded pulses and received from the transmission line. A compensation filter compensates distortions of the transmitted signals. A full wave rectifier circuit generates unipolar output signals. A pulse detection circuit derives rectangular pulses from the unipolar output signals. A phase-locked loop (PLL) circuit reconstructs a clock pulse train from the rectangular pulses. The transmitting unit receives an outgoing serial data stream from the telephone apparatus and internal clock pulses from that PLL circuit and includes means for converting the pulses of the outgoing data stream into AMI encoded signals.