METHOD AND SYSTEM FOR COMMUNICATION CHANNEL EXCHANGE

PROBLEM TO BE SOLVED: To provide a method and system for communication channel exchange by which an ISDN terminal is connected to an ISD network in a 64 kbps digital communication mode, without having to revise the configuration of the existing ISDN terminal operated in the high speed communication mode. SOLUTION: ISDN terminals 1, 2 are existent terminals to which a primary group speed interface is applied. A setup request for calling in the high-speed communication mode sent by the ISDN terminal 1 is received by an ISDN terminal 3 and a call request by number of channels in response to the designated transfer capability is sent to an ISD network 5. The ISD network 5 sends an incoming call request to an ISDN terminal 4 on each call request, and the ISDN terminal 4 returns a reply to the ISDN terminal 3 on each incoming call request. When incoming call requests by number of channels are received, an incoming call request in the high-speed communication mode is made from the ISDN terminal 4 to the ISDN terminal 2 and when a reply to this is returned, a reply is returned from the ISDN terminal 4 to the ISDN terminal 1 via the ISD network 5 and the ISDN terminal 3 and the ISDN terminals 1, 2 are connected to attain the communication.