To display the value of a parameter indicating the state of a communication channel without using a large-sized display part like a CRT, etc.

The value of the parameter indicating the state of the communication channel is measured by a channel state measuring part 20A and an item of the parameter to be displayed is selected by a display switching part 20D. In addition, a table indicating correlation of the item, a measured value of the parameter, frequency of flickering a flickering part 20F is stored in a table storage part 20B. And the frequency of flickering is calculated by referring to the table based on the item and the measured value of the parameter by a flickering signal generating part 20C. The flickering part 20F is controlled and flickered based on the frequency of flickering by a flickering control part 20E.