Abstract: In a communications system, channels can be assigned during an off-peak period with a lower pre-emption priority than normal channels, and may be pre-empted in favour of normal channels when insufficient channels are available. During a peak period, only normal channels can be assigned. A pool of available channels is maintained above a minimum level by pre-empting lower priority channels. Lower priority channels can be assigned from the pool only when it is above a threshold size. An advantage of this method is that channels can be assigned to noncritical applications during the off-peak period without substantially affecting the availability of channels during the peak period, thus encouraging more efficient use of off-peak channel capacity.