Question:
Where do you get the conference handle from that you are trying to add to? What it one that you created from TAPI or was it created as a result of user activity on a phone set.  If the latter, do you tell TAPI that the participants are related to the conference call?  What happens if you call lineGetConfRelatedCalls() on your conference call and/or participant calls?

Answer:
Any info on this will be greatly appreciated.

Two things: First, are you using conference correctly, setting it up using lineSetupConference and lineCompleteTransfer?  Are you sure you are passing it the conference call handle when it asks? Second, remember the difference between hdCall and htCall.  The reason that TAPI may return that error message when it detects that htCall is invalid. I'm curious, is TAPI even calling TSPI_lineAddToConference at all, or is it failing the TAPI call from the beginning?

I have to disagree: you are describing (correctly) *one* way of making a - conference. - But the way Manish did it (see TAPI-Test log in his posting) is generally - correct too. TAPI is going to haunt me the rest of my days, isn't it?  I didn't realize that there was more than one way of doing it.  We're not planning to put in Conferencing support into our TSP for another month, but while we are on the topic, let me try and get clear how you can do conferences.

Method 1, 2, 3: lineSetupConference -or- lineSetupTransfer -or- lineHold lineDial -or- lineMakeCall (depending on whether you have consult call already) lineCompleteTransfer

Method 4,5,6: lineSetupConference -or- lineSetupTransfer -or- lineHold lineDial -or- lineMakeCall (depending on whether you have consult call already) lineAddToConference

We do allow calls that are ONHOLD and ONHOLDPENDTRANF to put into conference, not just ONHOLDPENDCONF.

In other words, you do not have to use the consult call that was created, any will do. In other words, lineSetupConference lineDrop lineMakeCall lineCompleteTransfer