Abstract: A plurality of subscriber stations is connected to one or more PCM multiplex lines of a PCM switching network via a unidirectional loop and a transfer station. The subscriber stations are series connected to the loop on which addressed telegrams circulate originating and ending at the transfer station. The subscriber stations receive the telegrams addressed to them and exchange them for transmission to the transfer station. The transfer station transmits a time-slot received on the PCM line as an addressed telegram and vice-versa. For enhancing reliability all subscribers can be connected via a second loop and a second transfer station to one or more further PCM lines.

Abstract: A closed unidirectional transmission loop has plural stations coupled thereto in series for transmitting time multiplexed signals in the form of addressed byte groups. For transmitting a byte group, a station delays at the end of the byte group passing on the loop the following byte groups and introduces the byte group to be transmitted into the space resulting from the introduction of the delay. As soon as a byte group that is being or has been received by its addressee arrives at the station, this station removes the delay, thereby eliminating the byte group and thereafter can send the next byte group.