Wireless telegraphy

Uncommon card · No. 181833

Wireless telegraphy or radiotelegraphy is the transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code. Radiotelegraphy was the first means of radio communication, with the first practical radio transmitters and receivers invented in 1894–1895 by Marconi. Beginning about 1908, powerful transoceanic radiotelegraphy stations transmitted...

Read on Wikipedia · Image Photograph was taken by the U.S. Army Signal Corps, photo number: GHQ SWPA SC 43 5901 by T/4 Harold Newman., Public domain