Then just register the TS to the VCS using SIP in the same way you would a normal endpoint, and if you create a conference and give it a numeric ID, this numeric ID should be registered with the VCS.
Assuming you're running at least TS 2.2, CUCM 8.5 and CTS 1.7.4, that's all you need to do - you should now be able to make calls between them. If you're running older versions of any of these then you'll need to preconfigure each CTS in the TS web interface before you can call it as Cristian says above - more details of this are available under "Support for TIP endpoint identification and ad-hoc TIP calls" in the TS 2.2 release notes,
I'm not able to access my old voice mail messages all of a sudden. The recording says something like 'the message is currently not available'. This has never happened before in all the years I have been using this system. I have t...