This consists of a large piece of white cloth about twelve feet square spread out on the ground and three strips of white cloth twelve feet long and a couple of feet wide. These strips are laid in different positions relative to the square and each position has a number that means an order which the observer in the airplane also knows.
Further a small black square about eighteen inches on the side is placed on the big white square so that the observer can tell which battalion the outfit belongs to. The different positions of the strips and square are given numbers and the panelmen as well as the observer know what order each number means. As the panels can be arranged in twenty-seven different positions it is just about as hard to learn the panel code as it is the Morse alphabet.
Now as soon as the wireless apparatus has been set up the panelmen put out their big square and one strip at the end of it, and when