Explosion-proof signalling horn
Alarm horns as audible signaling devices are devices that are used to generate acoustic signals. Depending on the construction, alarm horns are powered with electric energy or compressed air. In the fire-protection technology, in fire extinguishing systems with gaseous extinguishing agents, alarm horns are used to announce a finished or imminent flooding of the protection area. You can also use alarm horns, for example, in process control to signal that certain thresholds have been exceeded. In electrically operated signal horns or sounders, a steel diaphragm is responsible for sound radiation. Together with an iron block, which closes the magnetic circuit, the membrane also forms the mechanical resonator. The fundamental frequency of the horn is determined by the mass of the iron block and the restoring force of the membrane used. Often, an additional horn is mounted for effective sound emission. The shape and material of the steel membrane determine, in addition to the internal cushioning and the spring characteristics of the system, the range of harmonics and the sound character of the horn. In contrast to electrically operated alarm horns, pressure horns operate acc. to the principle of a cushion whistle or the principle of a valve periodically closed by the flow. Some of the compressed air-operated alarm horns have a diaphragm which detects the flow and closes the valve.