Air Raid Signal

An air raid signal is a civil defense system that generates a loud warning sound for people to hear so that hopefully, they can get out of danger. Different from the EAS, it's not over airwaves or signals, but it is itself a signal that can be heard in the local vicinity of an attack, usually and most probably, incoming enemy attack from the air.

The system itself consists of a series of sirens, each set up high on a pole that, in the event of an emergency, warn hearers within in a radius of about 2 miles. Such signals are intended to be used in times of war to give warnings of incoming planes or of nuclear missiles should that be the case. They serve also to warn cities of impending natural phenomena such as tsunamis and tornadoes.

It possible that sometime in the near future, as much of our technology goes “wireless,” warnings of such events may be received on televisions, radios, smoke detectors, cell phones, or any other type of digital communication device that can receive a compatible signal from a remote location. In addition to various tonal capabilities, civil defense sirens today also have the capability of broadcasting digital voice messages.