I have run into two instances recently when using DMG2000 series gateways to integrate with OCS there is a delay when making calls to the PBX/PSTN.
You call a PSTN number from Communicator, the user on the other end answers the call however your communicator does not show the call as answered. Sometimes this will answer after 5 seconds or so, other times it will not answer at all. The fix is a simple setting in the dialogic configuration.
The Dialogic gateways have a setting under TDM->T1/E1 called ISDN Answer Supervision Enable. By default this setting is “Yes”. If set to yes the gateway will wait for voice activity to answer the calls, if set to No it will only listen to ISDN Messages.
This seems to only be the fix when you are making outbound calls to the PBX or PSTN, the inbound call answer delays are another issue. There are two things I have run into relating to delays when a MOC user is answering an inbound call from the PBX.
1. Make sure the Dialogic firmware is the newest version ( needs to be at least 6.0128 for OCS 2007 R2)
As of this posting this is the latest DMG2000 firmware available on the Dialogic website.
2. Make sure the RFC 3960 Early Media Support setting under VoIP->Media is set to Always
3. Make sure Voice Activity Detection is set to Off