Morse code

The duchess sat at a replica radio to hear, learn about, and decipher morse code.

Invisible ink makes an appearance in the complaint as does Morse Code, which, of course, is pretty uncrackable.

The alphabet of signals employed is the 'Morse code,' so generally in vogue throughout the world.

The Morse Code of Signals is not hard to learn but it requires much practice to "receive" even when the message is sent slowly.

Communication by the Morse code, or other special codes, may be carried on between submarines up to a distance of several miles.

Think of the things you learned in winning those twenty badges—the Morse Code, life saving, carpentry work.

We relieved the monotony a little by whistling to each other in the Morse code what we thought of the Huns for putting us there.