Communication network capable of automatically informing a subscriber of occurrence of an idle channel

In a communication network comprising a base station and a plurality of substations communicable with the base station through radio channels including a control channel, at least one of the substations comprises a memory unit (31) for storing an identification signal representative of an off-hook subscriber when no idle channel is found out in the radio channels. When an idle channel is detected by an idle channel detector (24), the identification signal is read out of the memory circuit to be sent to an idle channel notification cir, cuit (32). The idle channel notification circuit automatically informs the off-hook subscriber of occurrence of the idle channel through a subscriber interface circuit (16) by the use of a specific ringing signal. Alternatively, the identification signal may be sent from the substation to the base station and returned back to the substation so as to avoid collision among off-hook subscribers.