I need to verify if Cisco routers can do Nortel PBX "MCDN Emulation" with D-channel signaling. Want to give the PBX a signal that will tell it that the circuits are busy on a WAN link when a Voice call tries to go through. Using 2620 and 3660 routers connected with T-1's to Option 11's at remote ends and T-1 WAN links from main site.