PURPOSE: To selectively and exclusively utilize a part of or all of service(s) being possible to be provided for a private branch exchange.

CONSTITUTION: The private branch exchange having an additional number dial-in function is provided with a first register part 6, an indexing means 8 which indexes the first register part 6 by a received password so as to obtain service identification information, a second register part 10 and a judging means 12 which judges whether second service section identification information obtained by indexing the second register part 10 with a received additional number belongs to first service section identification information obtained by the indexing means 8 or not. A system is characterized by setting a pass as against the received additional number to a network 2 by a pass setting means 4 when result judged by the judging means 12 is positive.