http://www.controlbooth.com/forums/sound/18034-ringing-phone.html

We have used a standard ring voltage generator that I bought from a telephone supply house a few years back. I rigged a butt box (project box) with seven buttons (this was not for Belles but for a different phone intensive show. Each phone button were tied together on the "hot" side and each phones green was tied back to a "common" on stage. But, whether using the ring gen and butt box or our reglar low volatge (door bell generator) unit, the problem we have had is that with a two wire circuit, the phone continues to ring even when answered (overcome by sound operator timing it with the actors movement). So we never had a problem with the actor having it off hook.. (except if it was noticible to the audience that it "shouldn't" ring when it did...