Nice pix, Fred. In the background of the first image of post #9, the Germans are using a sound locator. One operator would look for the direction of the sound while the other determined the altitude. An American version: View attachment 23626 More on the subject: http://www.skylighters.org/howalightworks/ http://www.skylighters.org/
A BOAC Douglas DC-3, silhouetted by night at Gibraltar by the batteries of searchlights on the Rock, as it is prepared for a flight to the United Kingdom. Compressed (beautiful) image at: https://en.wikipedia.org/wiki/BOAC_Flight_777
just inserting a naval application: HMCS Prince Robert illuminating the german merchantman Weser off Manzanillo, Mexico, September 25, 1940.