Sirens (alarms)

stationary part of a rotary system

loud noise-making device

thumb|right|Two roof-mounted diaphone foghorns at [[Split Rock Lighthouse]] A foghorn or fog signal is a device that uses sound to warn vehicles of navigational hazards such as rocky coastlines, or boats of the presence of other vessels, in foggy conditions. The term is most often used in relation to marine transport. When visual navigation aids such as lighthouses are obscured, foghorns provide an audible warning of rock outcrops, shoals, headlands, or other dangers to shipping.

audible signal for emergency population warning

U.S. company specializing in emergency lighting, sirens, industrial equipment, and public safety equipment