PURPOSE: To discriminate simple whether or not the state of a circuit is satisfactory by permitting a radio station, when the station is in a state other than a communication state, to receive a control signal form a base station and subject a control signal to a prescribed decoding process including an error correction while counting correction errors in a prescribed period of time.

CONSTITUTION: A base station 10 transmits a prescribed control signal DP to all radio stations 10 through a control channel. Meanwhile, the radio station 20 is receiving a signal DP from a base station 10 at all time when the communication channel is out of a communication state. A CPU 26 effects a prescribed decoding process including error correction to the received signal DP. At the same time, the CPU 26 counts correction errors in a prescribed period of time and displays the result of counting on a display section 24. Thus, it is possible to decide exactly whether or not the circuit is in a satisfactory state.