The two "standard" signals that have been adopted in most communities are these:
THE ATTACK WARNING SIGNAL. This will be sounded only in case of enemy attack. The signal itself is a 3- to 5-minute wavering sound on the sirens, or a series of short blasts on whistles, horns or other devices, repeated as deemed necessary. The Attack Warning Signal means that an actual enemy attack against the United States has been detected, and that protective action should be taken immediately. This signal has no other meaning, and will be used for no other purpose.
THE ATTENTION OR ALERT SIGNAL. This is used by some local governments to get the attention of citizens in a time of threatened or impending natural disaster, or some other peacetime emergency. The signal itself is a 3-to 5-minute steady blast on sirens, whistles, horns or other devices. In most places, the Attention or Alert Signal means that the local government wants to broadcast important information on radio or television concerning a peacetime disaster. (See Chapter 1 of Major Natural Disasters section of this handbook.)
What To Do When Signals Sound
1. If you should hear the Attack Warning Signal--unless your local government has instructed you otherwise--go immediately to a public fallout shelter marked like this, or to your home fallout shelter. Turn on a radio, tune it to any local station that is broadcasting, and listen for official information. Follow whatever instructions are given.
If you are at home and there is no public or private shelter available, you may be able to improvise some last-minute protection for yourself and your family by following the suggestions in Chapter 5 (pages [33]-[38]) of this handbook. As a last resort, take cover anywhere you can.