In multiplexing, a predetermined bandwidth is reserved for each of the logical channels, the sum of which for all the logical channels equates the bandwidth of the line. In practice, none of the logical channels is fully utilized at all times by the equipment attached to them. Consequently, if the bandwidth of each of the channels could be dynamically adjusted according to its traffic, then some cost savings could be achieved by using a lower capacity line. For example, a 9600 bps line could beused to serve 10 times 2400 bps channels, assuming that no more than 4 channels are used at any one time.