PURPOSE: To attain information transmission over a wide range by installing a reception range partly to a stationary station in duplicate and devising signals from all stationary stations to be sent to a main station through wired line through a circuit selection device.

CONSTITUTION: The reception state of plural stationary stations receiving transmission data from a mobile station 1 is judged by a selection device 4. Then a stationary station 2 having a best transmission state is selected and a transmission circuit with the station is set and the line with other stations is interrupted. After the link establishment is finished, a communication text is mutually sent. That is, the communication is implemented mutually between the stationary station 2 and the mobile station 1. However, the position of the mobile station 1 is not constant, the link once established might be inadequate depending on a transmission reception capability. Then the reduction in the transmission level is detected by the selection device 4 and a link with a stationary station 2 with a highest transmission level at that point of time is selected. Thus, the mobile station 1 sending a weakest radio wave is traced.