PURPOSE: To minimize the traffic of a control channel and to shorten a duration by switching to other call channel at the time of the completion of one incoming action and executing continuously a bell ringing processing.
CONSTITUTION: By the receiving of telephone circuits 101∼103, a timer is set and an incoming call is separately sent to radio telephone sets 2∼5 when a control channel is idle. Respective telephone sets send an incoming call responding signal and switch it to a call channel. When a master device 1 detects a response from respective telephone sets or the timer overflows, the device switches it to a call channel, and when the receiving is one line, a bell ringing signal is sent and when the receiving is two lines or above, the bell ringing signal and another call channel designating signal are sent.