The various instruments used by signallers in transmitting messages on the Western Front during the First World War. In the left hand top corner are the aerial cables conveying telephone or Morse code messages. The lines are laid on the ground or buried near the firing line. Next is the Begbie lamp for flashing Morse code messages. Then two kinds of flags - one white and another blue - for use against light or dark backgrounds. An electric lamp on a tripod stand is used at night. Two types of flap or disc instruments follow. They are opened and shut with the long and short pauses of the Morse code. The one with the three flaps attached to a spring can be attached to a tree or wall. Then comes the much more familiar heliograph with its mirrors, which, of course, require sunshine to transmit messages. Finally, there is a whistle, which can be used for signals with Morse or other code.