RADIO SYSTEM

PURPOSE:To improve the availability of channel and to reduce the work at a base station for the improvement of the availability when mobile stations are close to each other in a radio system consisting of mobile stations and the base station. CONSTITUTION:After a mobile station in line-connected to a base station, the control device 38 of the base station transmits a test instruction as to whether direct calls are possible to mobile stations 1, 2 or not by using a transmitter 31. The controllers 16, 26 of the mobile stations 1, 2 alternately perform the transmission and reception by designating channels by controlling transmitters 11, 21 and receivers 12, 22 and test whether direct communications are right or wrong and the base station receives the results by receivers 33, 34. The base station set the channel for direct communication and a communication possible time value to mobile stations 1, 2 via transmitters 31, 32 and terminates the repeating operation to the mobile stations 1, 2. The mobile station starts the direct communication on a designated channel.