Electronic sirens are siren alarm systems that are just perfect to produce strong audible signals in case of emergency or to warn about imminent critical situations. A siren is a warning device which makes a long, loud, wailing noise. Most fire engines, ambulances, and police cars have sirens. In short, it means that something life-threatening is happening and you should go indoors and get more information. The specific guidelines (tornado, hail ,wind, etc.) for sounding sirens varies by jurisdiction, so check with your local community to find out the specifics if you are interested. 2.
A disk with evenly spaced holes around its edge is rotated at high speed, interrupting at regular intervals a jet of air directed at the holes. The resulting regular pulsations cause a sound wave in the surrounding air. The siren is thus classified as a free aerophone. A siren is a circuit which uses two transistors the NPN and PNP to produce a high frequency by using a speaker, the output of high frequency will be vibrating the speaker at high frequency hence producing a very sharply sound.
As siren provides alertness from danger, it gives enough time to the occupants to escape instead of individually going to each person to ask them to escape. There are two different tones used by Outdoor Warning Sirens: Attack: The signal for enemy attack is a rising and falling tone heard for 3 minutes. Civil Emergency: The signal for a civil emergency (such as a tornado) is a steady wail heard for at least 3 minutes.
