Abstract: The system switches first lines, each having a circuit mode channel and a packet mode channel, second circuit mode lines and third and fourth packet mode lines. The first lines are connected to subscriber equipments, each of which convoys both multiplexed channels which have a rate equal to that of the other lines. The second and third lines are connected to outside switching networks while the fourth lines are connected to a packet switching network. The number of the fourth lines is less than the sum of numbers of first and third lines. The fourth lines convey packets for all the connections established between two first lines or between a first line and a third line, or between a first line and the packet transmission medium served by the switching network. The system distinguishes the circuit mode channel and the packet mode channel in a first line.