PURPOSE: To lessen the distance limitation given by the Nyquist space and thus realize the regeneration of the burst row at a remote place, by giving compression to the burst space with every fixed unit number of the burst row before transmission and then giving the expansion conversion opposite to the compression conversion to the converted burst row received.

CONSTITUTION: A pair of two-wire system subscriber lines are used alternately in time division for both the transmission from the station to the subscriber's terminal and vice versa. And in case the digital signal of the aural signal is transmitted in both ways via the two-wire system, transmission bursts 7∼9 and 26∼28 of burst row S1 showing the sample information to be transmitted are compressed for the burst space with every fixed unit number to be converted into transmission conversion burst groups 13, 21, 38 and so on. These converted burst groups are transmitted to both ways in time division and via the two-wire system, and the expansion conversion opposite to the compression conversion is given to the burst space of reception conversion burst groups 14, 22... received in order to secure the regeneration into reception bursts 23∼25 and 35∼37 of burst row R1.