Packet and circuit combined exchange system

PURPOSE:To improve the efficiency of use of interoffice trunk lines in a packet and circuit combined exchange system, by specifying the uses of the individual interoffice trunk lines according to traffice without fixing them. CONSTITUTION:It makes to difference whether interoffice trunk line trunks 3 and 4 are used for circuit exchange or packet exchange. A controller 10 monitors the traffic of the circuit exchage and that of the packet exchange all the time and, according to the traffic, controls a channel switch 2 to connect one interoffice trunk line trunk, e.g., the trunk 4 to a packet composing and decomposing circuit 5 via a modem 6, thus using the trunk 4 for the packet exchange. The trunk 3, on the other hand, is used for the circuit exchange. Therefore, if an origination connection request is sent from a data terminal 8, the packet composing and decomposing circuit 5 is connected via modems 9 and 7 through the operation of the channel switch 2, and further connected to the other station via the trunk 4.