Paging channel control method and apparatus

In a messaging system, message traffic is transmitted on one or more traffic channels (T1, T2 ) and the allocation of groups (S1, S2 ) of receivers to the traffic channels (T1, T2 ) is controlled by information transmitted on a bulletin board channel (BB). A predetermined number of frames before a change in the traffic channel allocation, a countdown value is transmitted in the relevant traffic channel (T1 ) and the countdown value is decremented in each subsequent frame. Before the countdown value reaches zero, the groups of receivers (S1, S2) retune to the bulletin board channel, receive their new channel allocations and retune to the traffic channel indicated for their group. The frame timings of the different traffic channels (T1, T2 ) are staggered to reduce the peak power required to transmit message bursts in these channels.