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Wireless telegraphy

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Wireless telegraphy demonstration apparatus (Braun system)

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Firm Seeks to Surface Titanic's Wireless Telegraph

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Bing wireless telegraph

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How wireless telegraphy worked - Titanic case

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Titanic - Deleted Scene : The Wireless Room & The Californian

Wireless telegraphy means transmission of telegraph signals by radio waves; a more modern term for this is radiotelegraphy. Due to its simplicity, radiotelegraphy was the first means of radio communication; the first radio transmitters and receivers invented in 1894-5 by Guglielmo Marconi used radiotelegraphy. It continued to be the only type of radio transmission during the first three decades of radio, called the "wireless telegraphy era" up until World War 1, when the development of amplitude modulation (AM) radiotelephony allowed sound (audio) to be transmitted by radio. 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.
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