Atari XDM121 printer help

I just recieved an Atari XDM121 printer, and it appears to work fine, though is in need of a new ribbon. It is a daisy wheel printer, 80 column, and is set up to connect to the Atari 8bit I/O bus. It appears to have been produced in the mid to late 80's since the style of the case and buttons on the front are the same as those of the Atari ST line of computers, and not the earlier 8bit machines (ie. the case is grey and the 3 buttons on the front panel have diagonal vertical lines). My question is about a third connector on the back (the other two being the 8bit I/O bus connectors). This third connector is a modular connector, similar to a RJ-11 phone jack, and it has just two contacts in it. Any ideas on what this might be for? Any help would be greatly appreciated. Thanks. Jeff jeffh(a)unix.aardvarkol.com -- ---------------------------------------------------------------------------- Amiga enthusiast and collector of early, classic microcomputers http://www.geocities.com/siliconvalley/lakes/6757