For use in a common service area of a plurality of radio base stations, each being preassigned with a radio channel and for transmitting a channel status signal indicative of whether the radio channel is idle or busy, a terminal station (14) comprises a monitoring circuit (37) for cyclically monitoring the channel status signals of the respective base stations to produce an internal signal when the radio channel is found idle for one of the base stations that has a highest priority for the terminal status. Responsive to the internal signal, a control circuit (29) inhibits the cyclic monitoring for other base station or stations. The priority is decided by a measuring circuit (27) for measuring field intensities of the respective channel status signals. When the base stations are three in number, operation of the monitoring circuit is inhibited for the channel status signal of a lowest-priority base station when both radio channels of two other base stations are idle.