When an incoming ISDN call over a trunk with NCT-type PSTN service is answered at a station or voice response unit (VRU), the station user or VRU places the call on hold, and dials the number for a PSTN of VPN endpoint where the outgoing trunk B-channel is determined by AAR or AAS routing. The station user initiates a call transfer using the Transfer feature button or a switch hook flash, or the VRU initiates a call transfer by using an analog or line-side E1/T1 switch-hook flash.

The switch automatically sends an invoke NCT FACILITY message when the transfer is completed if the following conditions are met:

• The Network Call Redirection field is set to y on page 3 of the System Parameters Customer Options screen.

• An NCT-type protocol is administered for both the incoming and outgoing call ISDN trunk group.

• The second leg call is eligible for redirection by means of an NCT-type protocol, which requires for the MCI NCT and TBCT protocols the second leg of the call is in the same trunk group and has the same signaling group as the incoming call. For the NCR ETSI ECT protocol, the second leg of the call can be over a different trunk group with a different signalling group than the incoming call leg.

If the station user or IVR initiates and completes a three-way conference instead of doing a call transfer operation as above, and releases or hangs up from the conference with the following condition also being met, the switch automatically sends an invoke NCT ISDN message to the PSTN or VPN switch if also the following condition is met:

• The number of parties in the conference including the conference originator must be no greater than three parties.