Missing diverting party on NEC DMG1000

Symptom

When installing a Dialogic Media Gateway Series (DMG1000) digital set emulation gateway in an NEC PBX environment that is distributed over a large area using IP TIE trunks, diverted calls can arrive to the gateway missing their called (diverting) party information.

Reason for the problem

This condition is due to the way that the NEC PBX presents called party data to the display on a digital station set.
Refer to the diagram below to follow the call scenario. 

The scenario has two users: User A on one PBX at extension 1234 and User B on another PBX at extension 5678. User B calls User A, User A is not at his/her desk and his/her phone forwards because of a ring no answer forwarding condition to the gateway configured on a third PBX. All the calls are done across the various PBX segments over IP TIE trunks. 

Traces gathered on the gateway show that the display for the call looks as follows:

Open

295:21:736 [Adept-8 ] Code [ FDA TIE
295:21:736 [Adept-8 ] Code 5678 ]

The call arrives at a port of the gateway and is missing all data referring to User A, but still contains the reason data, so the call appears as if it is a direct call. This lack of information causes the voice messaging system to not properly integrate this call. Typically, the caller will hear the main greeting of the voicemail or, if the caller is a user on the system, may be asked for his/her password to log in to his/her own mailbox.

Fix / Solution

The PBX in this configuration is limited in the data that it will present to the display of a digital station set. The solution to this limitation is to use the NEC’s serial integration link instead of the digital station sets capability to gather its integration information via the emulated digital display. The MCI link will carry the information needed to properly integrate the call in this configuration. 

You can use the serial integration link for both analog and digital set emulation gateways, so if you have been using a digital set emulation gateway and encounter this limitation, you can continue to use it or change it out for an analog unit.