I've seen the 7700 phones act a little funny with the 616's and older 624 versions. When the Intercom button is pushed it gives you intercom tone for about a second then it goes away.

I think that if you make dss buttons to intercom, then it will work Ok.

Nobody remembers those big yellow stickers on the 7700 boxes that warned about using them with 624's -4 or below?

Aaron