[cisco-voip] Call Manager+IOS-GW+Conferencing

[Bob A. Bowie]

I have a cluster Call Manager 4.1.3 and a cisco 3700 IOS Gateway to a PBX.
I can conference IP Phones on the Call Manager all day long.  However, when
I try to conference in a phone on the PBX, the IP Phone says "No Conference 
Bridge".
Why is this happening?
Also, would there be any issues the pther way with a PBX phone trying to 
conference multiple
IP Phones on the Call Manager?

Thanks,
Bob