I was told about a call to my office today, for this same problem, from a government office. I'm assuming it was the same office, but the person's name was different.

The way my dispatcher described the caller's problem, it sounded like the Voicemail Monitor feature that was causing the ring burst, and they said it happened even with DND turned on, such as in the conference room. If it's only the conference room that's concerned, why not get rid of the mailbox for the extension. Another option could be to get rid of Call Forward Busy/No Answer for the particular station, so no calls go to voicemail for that station? Other than that, if it is, in fact, the Voicemail Monitor feature that we're talking about here, I don't know of any way to turn it off for the DX80/120. The other Comdial systems allowed you to toggle the Listen/Pickup feauture on and off in voicemail programming. They didn't have that option in the DX80/120 voicemail, and the Voicemail Monitor timer can't be set to zero.