I've setup Ad-Hoc conferencing on a 2811 running 12.4(15)T8 with CME 126.96.36.199. Using phone 1 I call phone 2 and then on phone 1 I place phone 2 on hold. Then I make a new call from phone 1 to phone 3. At that point I press conference on phone 1 and phone 2 and 3 are joined in a conference and phone 1 shows that it is connected to the extension that I have defined as the conference extension. However, I hear a busy signal on phone 1. Phones 2 and 3 can communicate back and forth just fine, but phone 1 doesn't become part of the conference. Phone 1 and 2 are on the same CME and phone 3 is on another phone system that communicates via H323. The conferencing is setup as hardware on the 2811 and I have enough PVDM2 resources to allow 6 sessions. I don't understand why phone 1 doesn't become part of the conference.