Abstract: A system which includes an exchange (EX) to which are connected a plurality of telephone sets (TA). The exchange contains a central processor (EXCP), a plurality of line boards, each of which contains a plurality of line circuits (DEC) for interfacing between the exchange and the connected telephone sets. Each telephone set contains a line circuit (DIC) in which there are included a coder and decoder for PCM-coded information words. The system is completely digitized and transfers digital information in time-divided form between the telephone sets. For achieving accurate synchronization of the pulse trains between the different units while simultaneously reducing jitter, the unit (DIC) is equipped with a counter (CTP.sub.T) which under control of a signal from a comparison circuit (CO) is reset to zero at given times, thereafter starting counting once again with synchronizing signals defining a synchronizing window being sent via a line to a receiving unit (DIC) in a telephone set.

Abstract: A method and an arrangement for reducing the demand on the number of transferred bits when transferring PCM information. Polarity and amplitude information are transmitted from a transmitter side to a receiver side, expressed by binary code words, while a chosen upper limit in the amplitude code word indicates transition to a segment having a higher number and a chosen lower limit in the amplitude code word indicates transition to a segment having a lower number. The limit values are transmitted to the receiver side and are used on the receiver side as well as on the transmitter side for generating counting signals. The counting signals are registered on the transmitter side and the receiver side for giving a value which expresses the associated segment. By means of the registered value, a control signal is generated in order to increase and decrease respectively the segment value of the transmitted signal.