From verso of card: "The duty of anti-aircraft searchlight units is to find and illuminate enemy aircraft so that they can be attacked by our own fighter machines or fired at by anti-aircraft guns. The searchlight has a glass paraboloiddeflector 36 in. in diameter and an electric arc lamp which gives a light of many millions of candle power. In fine weather the searchlight has a range of over 5 miles. The complete searchlight detachment consists of 10 men who work the searchlight, a sound locator . . . and a generating plant which provides the necessary power for the arc lamp."