The 4310ME Sentronic is a heavy duty, electrically controlled closer/holder designed to provide infinitely adjustable hold-open for fire and smoke barrier doors. Door is held open until current interruption releases mechanism and the door closes. Single lever (track) arm closer is specifically designed for interior doors. Built-in on/off switch controls the hold open function. Independent adjustment valves for adjusting backcheck, closing and latching speeds. Adjustable backcheck prevents damage to the closer, door and frame. Swing-free arm allows door to be moved without closer resistance. Functions as a full rack and pinion closer when hold open is not engaged or the current is interrupted. Closer cylinder constructed of high strength cast iron, full complement bearing, 1-1/2" diameter piston, and 11/16" diameter double heat treated pinion journal. Interfaces with fire alarm systems.