Vehicle horn England, developed a standard electric car horn in 1910. Car horns are usually electric, driven by a flat circular steel diaphragm that has an electromagnet acting on it in one direction and a spring pulling in the opposite direction. The diaphragm is attached to contact points that repeatedly interrupt the current to that electromagnet causing the diaphragm to spring back the other way, which complete the circuit again. This arrangement opens and closes the circuit hundreds of times per second which creates a loud noise like a buzzer or electric bell, which sound enters a horn to be amplified. There
Muster drill trips on the water, such as those taken on ferries, dinner cruises, and riverboats. On ferries, a safety briefing delivered through the PA system alerts passengers to the sound pattern of the emergency alarm and what to do if the signal is heard. Generally, the muster drill is taken in simple instructions: The "general emergency alarm" consists of seven or more short blasts followed by one long blast of the ship's horn or whistle (some lines don't sound the signal on the horn or whistle) and by the ship's internal alarm (such as fire alarm bells accompanied with flashing strobe