Communications system

A communications system comprising a first station capable of communication with a second station over a wireless channel, data being carried over the wireless channel in superframes, each superframe comprising a plurality of frames and each frame comprising a plurality of timeslots; the system having: a first mode of operation in which a full rate data channel for circuit switched communications is defined by the allocation to that data channel of corresponding time slots in each frame; a second mode of operation in which two half rate data channels for circuit switched communications are defined by the allocation to each of those data channels of an equal number of corresponding time slots of frames in each superframe; and a third mode of operation in which four quarter rate data channels for circuit switched communications are defined by the allocation to each of those data channels of an equal number of corresponding time slots of frames in each superframe.