Dial tone heard during Lync call

By |2017-12-04T11:14:54+00:00October 12th, 2011|Skype|0 Comments

This article was pointed out to me by a customer that has this exact issue whilst using FUS – Thanks Matthew Smile

Thought it was definitely worth a re-blog here:


Communicator/Lync issues with “Fast User Switching” on Windows 7

During work on OCS 2007 R2 and Lync projects, I have come across some strange behaviour on Communicator and Lync, this behaviour has only been noticed with computers accessed by more than one person – Often “Common Area PC”

When a user is logged on to a computer and has locked the computer and a new users logs into the same computer by using “Switch User” functionality, the new user are having problems using Communicator/Lync for any type of Audio calls.

If the user try to do a PSTN call there is a constant dial tone in the background and the call will eventually terminate.
If the user try to join a A/V Conference, there is no audio and the conference call will end.

Microsoft has confirmed – in mail – that there is an issue with FUS (Fast User Switching) and Communicator/Lync.
They have also done some investigation on this, but the change has been consider to large for the current available clients.

Work Around:
Since this problem/issue mostly occurs at “Common Area PC”, often meeting room pc, there is possible to turn off FUS on those computers. This can be done in GPO.

Another workaround would be to create a trigger that trigger’s on “Computer Lock” and terminates the Communicator process. The same trigger will trigger’s on “Computer Unlock” and restart the Communicator process.
This is probably NOT the best approach, but it will “solve” the problem.


My customer is simply going to get all users to logoff rather than switch when hot-desking which is more manageable given their environment.

Thanks to Trond Egil Gjelsvik-Bakke for the original blog!

Good luck


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