CD2200/Back-up (500 lb. capacity only) Electronic control system for winding drum mechanism Smooth ride Oiless operation Emergency battery back-up system available (raising and lowering) Back-up system is automatic switching with more than 75 round trip (2 stop) cycles on battery power Sleep mode extends battery life for months Patented Maximum travel distance is 50' Can be located in basement, attic or adjacent to shaft at landing (no overhead apparatus required) Call buttons on each floor Runs on 220v.lph house current