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wireless telegraphy
Wireless telegraphy is the transmission of electric telegraphy signals without wires (wirelessly). It is now used as a historical term for early ''radio'' telegraphy systems which communicated with radio waves, although when the term originated in the late 1800s it was also used for a variety of other experimental techniques for communicating telegraphically without wires, such as photoelectric and induction telegraphy.
Wireless telegraphy came to mean Morse code transmitted by radio waves (electromagnetic waves), initially called "Hertzian waves", discovered by Heinrich Hertz in 1886. The first practical wireless telegraphy transmitters and receivers were developed by Guglielmo Marconi beginning in 1895. By 1910 communication by Hertzian waves was universally referred to as "radio",〔(earlyradiohistory.us, UNITED STATES EARLY RADIO HISTORY THOMAS H. WHITE, s e c t i o n 22, Word Origins-Radio )〕 and the term wireless telegraphy has been largely replaced by the more modern term "radiotelegraphy". The transmission of speech (radiotelephony) began to displace wireless telegraphy by the 1920s for many applications, making possible radio broadcasting. Wireless telegraphy continued to be used for private point-to-point business, governmental, and military communication, such as telegrams and diplomatic communications, and evolved into radioteletype networks. Continuous wave (CW) radiotelegraphy is regulated by the International Telecommunication Union (ITU) as emission type A1A.
Today in the United States, as in much of the world, commercial radiotelegraphy is used far less than in the past. On shipboard the computer and satellite linked GMDSS system has largely replaced Morse as a means of communication. Telegraphy is taught on a very limited basis by the military.〔(Morse code training moving to Goodfellow )〕 A CW coastal station, KSM, still exists in California, run primarily as a museum by volunteers.,〔(Coast Station KSM )〕 and occasional contacts with ships are made. Radio beacons, particularly in the aviation service, but also as "placeholders" for commercial ship-to-shore systems, also transmit Morse but at very slow speeds.
The US Federal Communications Commission does still issue a lifetime commercial Radiotelegraph Operator License. This requires passing a simple written test on regulations, a more complex written exam on technology, and demonstrating Morse reception at 20 words per minute plain language and 16 wpm code groups. (Credit is given for amateur extra class licenses earned under the old 20 wpm requirement.)〔(TITLE 47—Telecommunication CHAPTER I—FEDERAL COMMUNICATIONS COMMISSION SUBCHAPTER A—GENERAL PART 13—COMMERCIAL RADIO OPERATORS )〕 Wireless telegraphy is still used widely today by amateur radio hobbyists where it is commonly referred to as radio telegraphy, continuous wave, or just CW. However its knowledge is not required to obtain any class of amateur license.
==History of development==
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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