Abstract: A telecommunication system is structured on a multi-plane basis, having an information transfer plane (3), and one or more other planes (4, 5). When a call is set up an initial connection is made via the first plane (3) in packet switched manner. If other services such as voice are needed, connections between the user's terminals are set up on a circuit-switched basis, under control of the connections already set up in the information transfer plane. These additional connections are only maintained as long as needed.Note that whereas connections are set up in packet manner in the information transfer plane, they are set up in circuit switched manner in the or each other plane.