PURPOSE: To prevent occurrence of a communication line acquired ineffectively by devising such a system that two-way communication lines in a line exchange are to be acquired by the number of lines designated by each multiple access call.

CONSTITUTION: A caller side line selection means 100 acquires selectively a communication line 310 sending information to a called line exchange 2 from its own line exchange 1 in a caller line exchange 1 by line number designated by a multiple call and informs the acquired communication line 310 to other line exchange 2. A called line selection means 200 acquires selectively a communication line 320 sending the information to the caller line exchange 1 from its own line exchange 2 in the incoming line exchange 2 by the number of lines designated by a multiple call and informs the acquired communication line 310 to the caller line exchange 1. Thus, the communication lines 310, 320 in two-way are acquired by the line number designated by each multiple call. Thus, the production of a communication line acquired ineffectively is precluded.