asterisk users - Sep 2004 - 3 Way Calling on Snom Phones and Asterisk

Has anyone been able to get 3way/Conference working with the snom200 and
Asterisk. According to the documentation for the phones the option should come
up when you have two lines active on the snom phone. Unfortunately, I don't
see this option appear and I am now beginning to wonder if this is a limitation
of Asterisk. Does anyone have any suggestions? Any help would be greatly
appreciated.

Thanks,
Brian