Does the Meridian 1 offer a 4 wire SF Trunk interface that could be used as a PBX Tie-Line? (Like the E&M Tie-Line). I have to install 30 tie-lines from my PBX to a Meridian 1 81C. I can only use one of four signaling methods (E&M Type 1, E&M Type 2, DX, or SF) All except SF would require down time for me to install in my switch. My customers don't tolerate down time so I gotta find a way to make this work.