Hello, Does anyone know if the 3CX pbx supports or interworks with host softswitches that support "Release Link Transfer" or "2 B Channel Transfer". These are typically ISDN trunk features which allow for the saving of trunk resources when a transfer is initiated. A typical situation is when A calls B, A is in the PSTN, B is a PBX extension. The call from A to B uses up a time slot on a ISDN trunk group between the PSTN switch and the PBX. After answering the call, B then forwards the call to C, C like A is on the PSTN. So now the 2nd leg of the call also uses another time slot on the ISDN trunk group. Since this is wasteful, with RLT/2B transfer the host switch would instead "bridge" the call between A and C and therefore releasing the 2 time slots on the ISDN trunk group. In the IP world this shouldn't occur since calls, at least the audio portion should be going peer to peer between endpoints if REFER along with the Replaces header is support by each endpoint. But in a Hybrid PSTN/TDM and SIP/IP world it probably depends on the interaction between the PBX and the host switch. Any thoughts?