Article ID: 968944 - View products that this article applies to.
In Microsoft Office Communications Server 2007 R2, Public Switched Telephone Network (PSTN) users are put on hold and music is played because the Presenter/Leader has not yet joined the conference. However, when enterprise users join the conference by using the Join link or by dialing in to the conference by using their extension number and PIN, they can start the conference call without the presence of the Presenter/Leader. The enterprise users can have the conference call without realizing that PSTN users are on hold.
To resolve this issue, apply the following update:
968913After you apply this update, PSTN users can join the conference as soon as an enterprise user has joined the conference. If no enterprise user or Leader/Presenter has joined the conference, PSTN users are put on hold and music is played.
(http://support.microsoft.com/kb/968913/ )Description of the update package for Communications Server 2007 R2, Conferencing Attendant: April 2009
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.