I think the Mitel Quick Conference system did that. That was one of my complaints I had with the system when I went through the online training for it. - no security -.
How many people do you need in the conference?
I think you can 'fake it' with up to 7 by programming an analog phone as a 'non-busy' extension and then strapping an 800ohm resister across T&R. Then when you call it you should be automatically joined in a conf call.
Also, just processing out loud here, you may be able to use the AWC and some very complex programming on the 3300. You'd have to set up a permanent conference and then program up an IP loop back trunk, with an ARS route that loops through the new loop back trunks. You'd use the digit mod table to actually enter the conference number. The result should be that the caller would just be dumped directly into the permanent
conference.
Ralph