Features: Pure copper electromagnetic coil with discontinuity and no electromagnetic interference. Strong tapping, stable operation and long service life. Hard metal shell, not easy to deform, the sound reaches 100db, and it is farther and safer. The surface is coated with electroplating technology to make the material more anti-corrosive and less prone to rust and corrosion. Portable wired power supply, easy to install, can be installed on the wall, ceiling and other installation methods. Choose 12V DC / 24V / 220V according to the voltage you use. Specifications: Condition: Brand New Color: Red Material: Metal Size: 4 inches(100mm) Power Mode: External Optional Voltage: 220V/12V DC/24V Alarm Volume: 100db Surface Treatment: Electroplating Package List: 1 * Fire Alarm Bell Package List 1 * Fire Alarm Bell 1Pure copper electromagnetic coil with discontinuity and no electromagnetic interference. 2Strong tapping, stable operation and long service life. 3Hard metal shell, not easy to deform, the sound reaches 100db, and it is farther and safer. 4The surface is coated with electroplating technology to make the material more anticorrosive and less prone to rust and corrosion. 5Portable wired power supply, easy to install, can be installed on the wall, ceiling and other installation methods.