Abstract: A method and apparatus implementing a large telecommunications network. A large Channel Group Switch is connected to a plurality of tandem switches and/or end office switches and toll switches. A route consists of all channel groups interconnecting two specific switches via the Channel Group Switch. Connections between a pair of channel groups in the Channel Group Switch are fixed as long as the pair of channel groups are assigned to the same route. The Channel Group Switch connects all traffic on one channel group to a particular other channel group. As traffic demands change, channel groups are assigned to different routes. In one preferred embodiment, the channel groups are DS-1 Groups of 24 channels each, a sufficiently small number to permit routes to be enlarged or decreased for the benefit of other routes. Advantageously, such an arrangement can be used to interconnect a large number of tandem switches efficiently.