New Air Raid Warning System
A poster providing instructions for the air raid warning system with the three columns 'When Signal is Given - It Means - You do This.' First is Blue Warning, a steady blast, meaning enemy planes headed in your direction. Second is Red Danger, a series of short or wavering blasts, meaning bombing expected. Third is Blue Warning again, meaning enemy planes have passed. Final line is White All Clear, a radio signal indicating danger is over. To the right of each line is a list of appropriate actions to take for each signal, and further information is at the bottom of the poster.