PURPOSE: To attain monitoring with simple control even when a mobile equipment is moved and a channel changeover takes place by providing a fixed talking path not affected by channel changeover with a reflection means and connecting the fixed talking path to a monitor so as to monitor the path.

CONSTITUTION: When a mobile station 7 makes a call via a base station 5, an exchange 1 retrieves a loopback means 3 to connect lines 5a, 3a with a path 10a and connects other line 3b of the loopback means 3 and a line of a trunk 4 of an outgoing connection side with a path 10b. According to a command of monitor connection, the exchange 1 connects the line of the monitor 2 and the line of the loopback means 3 with paths 11a, 11b. When the mobile equipment 7 moves to a radio zone covered by a base station 6, The exchange 1 sets a path 10a' connecting the line 6a and the loopback means 3. In this case, a channel is changed over and since the path 11b between the loopback means 3 and the monitor 2 is not revised, the monitoring is continued.