PSTN Incoming Call transferred to PSTN, and Trunk Usage

[pbarman]

When I receive an incoming call from PSTN to an IP Phone, and I transfer the call back to another PSTN number (so the IP phone drops at this point), the two PSTN numbers are now connected and talking to each other. The call still uses the PRI channels of our voice gateway that was used for the incoming and outgoing transferred call. A 6608 and h323 gateway behaves the same way.

Is there anyway we can avoid this so that when a incoming external call is transferred to an external number, it should release the channels of my gateway ???

[irisrios]

When the IP Phone transfers the call to another PSTN number, the CM initiates a new call towards the gateway and its something like box (gw) is acting as both OGW and TGW. Since it is a two different call, gateway will not know that it is a TDM hairpining call and hence it may not release its DSO's and DSP's. Even if it is TDM hairpining call, DSO's will still be used.