PURPOSE: To make it unnecessary to mount a loop back trunk exclusive for a simplex connection by providing a switch for changing a speech path with a voice repeating trunk between a radio base station and a switchboard, an switching this switch by a call connection type.

CONSTITUTION: When a radio terminal 2 calls to a radio terminal 3, a switchboard control device 12 knows from a dial number that a connecting destination is a radio terminal, that is the simplex connection, and the speech path of a voice repeating trunk 7 planning to be used in this call is connected like the solid line of a diagram (a speech path 7C). At the same time, the radio terminal 3 is called through a radio control channel. After the radio terminal 3 responds, a radio communication channel 4C and a voice repeating line 6A are connected, and a communication radio channel 4D and a voice repeating line 6B are connected.