Simplex 49SO-APPLW Wall Mount Addressable Speaker The Simplex 49SO-APPLW is a Wall Mount Addressable Speaker (S/O) notification appliance. This speaker uses a Simplex fire alarm control unit (FACU) IDNAC signaling line circuit (SLC) to individually power, address and control the Simplex 49SO-APPLW. Install wall mount indoor and addressable S/O notification appliances on standard 4 inch square 2 1/8 inch deep USA electrical boxes for flush installations, provided by others, or surface or weatherproof (WP) backboxes. NOTE: Select cover, mounting plate, and surface or WP box separately, if required. We are selling a huge amount of new alarm equipment! Please take a look at our other listings! Feel free to message me for an inventory list including other items that we haven't listed yet! *WE CAN WORK OUT A DEAL FOR BULK ORDERS* SHELF: B