1275CA without hush button A= 5-5/8", B= 1-5/8", C= 5-5/8" 1275HCA (AC12WH) w/hush button A= 5-5/8", B= 5-5/8", C= 5-5/8" Direct Wire, battery backup, 5 Year Warranty, single or multiple station capability up to 24 units, low battery indicator, fits all standard electrical box configurations, quick-disconnect, flashing red LED light indicates which unit in the multi-station is the originating alarm, green light indicates 120VAC power, FHA, HUD, UL, NFPA & California state Fire Marshal approved, AC/DC powered with battery back-up included, hush button optional