An end user at a remote site is trying to initiate an Ad Hoc conference call to an end user at the main site. The conference receives an error message on the phone: Cannot complete conference call…

When devices using different codecs attempt to join an ad hoc conference, a transcoder is required to convert the audio streams. If the transcoder resource is missing or unavailable, the conference bridge cannot process the mixed codecs, leading to a 'Cannot complete conference call' error.

If the remote phone did not have the conference feature assigned, it typically wouldn't allow the user to initiate a conference at all, rather than failing during the call setup with this specific error.

A software conference bridge must be assigned for ad hoc conferencing to function, and if it were entirely missing, the conference would not start, but the specific error points to resource availability during an active attempt.

A Media Termination Point (MTP) is typically used for DTMF interworking or to allow H.323 devices to connect to SIP-based conferences, but its absence would not directly cause a 'Cannot complete conference call' error related to codec issues in an ad hoc conference.