Copyright 2003 Call Processing 1. The D channel is used to send the called number to the local ISDN switch. 2. The local switch uses the SS7 signaling protocol to set up a path and pass the called number to the remote ISDN switch. 3. The remote ISDN switch signals the destination over the D channel. 4. When the remote router indicates that it will receive the call, the remote ISDN switch uses SS7 to send a call-connect message to the local switch. 5. One B channel is connected end-to-end, leaving the other B channel available for a new conversation or data transfer. Both B channels can be used simultaneously.
Copyright 2003 ISDN Functions and Reference Points