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.

Abstract: A synchronizing circuit for use with a digital communication system is disclosed. A serial data stream is arranged in frames composed of at least two data words containing a synchronization signalling code and binary coded information, respectively. For detecting the alignment of consecutive frames the synchronizing circuit includes a serial/parallel converter and a synchronizing detector logic network for generating two control signals indicating the presence of the synchronization code in form of a normal synchronizing bit pattern or an inverted synchronizing bit pattern respectively. An AND-gate logically links the first control signal delayed by one pulse frame to the undelayed second control signal and generates a synchronizing signal. A time slot generator produces enabling signals by means of counting subsequent system clock pulses under control of this synchronizing signal such that during receiving of different data words of a frame a respective one of the enabling signals is present.