Communication Needs

What communication technology was invented DURING world war one?

This is for my homework. I need to know what communication technology was invented DURING (not before or after) world war one. Please help! Thanks

Public Comments

1. Morse Code?
2. Seems Pigeons. http://www.firstworldwar.com/atoz/carrierpigeons.htm
3. Wireless communication was already invented by that time. Marconi Experiment : 1891
4. The Fullerphone (named after its inventor, Maj. Gen. A.C.Fuller ) was invented during WW1. It was a morse code communication used in the trenches. Below are a couple of links for more information.