PURPOSE: To conduct termination of a data link with little burden even when digital lines increase in the number by providing a multiplexing means for multiplexing data link received data of each digital line onto an intra-station link and a terminating means for extracting to collectively process the multiplexed data link received data of each digital line.

CONSTITUTION: When a frame synchronizing bit of a top frame of a multi-frame among frame synchronizing bits of respective frames of respective digital lines 101 is multiplexed, a multiplexing means 102 multiplexes discrimination data for indicating that the multiplexing timing is the top frame of the multi-frame at the same time. A terminating means 104 extracts data link received data of the respective digital lines 101 multiplexed onto an intra-station link 103 for collective processing. Namely, the data link received data, after being multiplexed onto the intra-station link 103 by the multiplexing means 102, are extracted by the terminating means 104 for collective processing. Accordingly, the cost of a switchboard and the like for terminating data links is suppressed at a low level.