BRK SA520B (model SA520) is a wire-in, 120V AC 60Hz single and/or multiple station photoelectric smoke alarm specifically designed for residential and institutional applications including sleeping rooms of hospitals, hotels, motels, dormitories, and other multifamily dwellings as defined in standard NFPA 101. BRK SA520B has been fully tested and complies with, UL217, CSFM, NFPA 72, and NFPA 101 and other agencies that model their codes after the above agencies. It meets building codes where AC with battery backup smoke alarms with wireless interconnect and silence features are required and with model building codes published by the ICC. BRK SA520B is a state of the art wireless smoke alarm designed to provide early warning of a fire. It features a fully insect screened Photoelectric smoke sensing chamber, an 85dB horn, a full function test switch and a silence feature. This smoke alarm interconnects via wired and/or wireless communication. Wireless communication is on a reliable and secure radio frequency of 915 MHz frequency with 65,000 security codes and 3 channel frequency hopping. It operates on a Mesh Network; a two-way communication format that sends, receives and resends the alarm signals providing a more reliable network. It also features tamper resistant locking pins that lock alarm to the mounting bracket and battery drawer to prevent removal of battery or alarm. Perfect for apartment, dormitory or hotel applications. Designed for wall or ceiling mounting.