MS-4 4-zone fire alarm control panels (FACPs) bring the latest in microprocessor technology to conventional fire controls. These FACPs are compatible with System Sensor® i3 smoke detectors with drift compensation, maintenance alert, and freeze warning. Automatic synchronization of audio/visual devices is provided with three selections for manufacturer protocol. The notification appliance circuit (NAC) protocol can silence audible devices while strobes continue to flash, using a single pair of wires. These FACPs are compatible with conventional input devices such as 2- and 4-wire smoke detectors, pull stations, water flow devices, tamper switches, and other normally open contact devices.