PURPOSE: To stably perform periodical speech audit, to perform center station call control, and to confirm signal communication between terminal mobile machines, by performing speech audit after switching a speech channel between radio exchanges by a mobile central radio exchange.

CONSTITUTION: The mobile central radio exchange 2 generates a base station control transmission signal ADV that is a speech audit request and analyzes a reception signal ARV. The speech audit can be executed by the transmission of the signal ADV and the reception of the signal ARV at a mobile radio exchange 3 and a base station 4. A message operation is performed by mapping the signals ADV, ARV on base station packetized data BSPDU.