Abstract: A bi-directional switching network for a telecommunications exchange in the form of a matrix array of symmetrical switching devices each having many terminations at opposite sides. The switching devices of each row individually have their terminations at one side multipled whereas the switching devices of each column individually have their terminations at the other side multiplied. In a preferred embodiment each switching device includes at least one switching module comprising A-switches, B-switches and a C-switch all of the relay-matrix type; the first two categories of switches being arranged in planes. Connections are usually established over an A-switch and a B-switch of an appropriate plane, but the C-switch is available for interposing between any A-switch and B-switch under heavy traffic conditions and provides for switching between planes.