Tuesday, November 20, 2007
WikiProject Telecommunications may be able to help recruit one. If a more appropriate WikiProject or portal exists, please adjust this template accordingly. The term Wireless Telegraphy is a historic term rarely used today except as applied to early radio telegraph communications. Wireless telegraphy originated as a term to describe electrical signaling without the electric wires to connect the end points. The intent was to distinguish it from the conventional electric telegraph signaling of the day that required wire connection between the end points. The term was initially applied to a variety of competing technologies to communicate messages encoded as symbols, without wires around the turn of the twentieth century with radio emerging as the most significant. These other competing wireless telegraphy technologies are interesting, but pale in significance. Wireless telegraphy rapidly came to be synonymous with Morse Code transmitted with electromagnetic waves decades before it came to be associated with the term radio. Wireless telegraphy is rarely used today except by amateur radio hobbiests where it commonly referred to as continuous wave (CW) radio telegraphy, or just CW.
Ground and water conduction
Both electrostatic and electromagnetic induction were used to develop wireless telegraph systems which saw limited commercial application. In the United States, Thomas Edison, in the mid-1880s, patented an electrostatic induction system he called "grasshopper telegraphy", which allowed telegraphic signals to jump the short distance between a running train and telegraph wires running parallel to the tracks. This system was successful technically but not economically, as there turned out to be little interest by train travelers in an on-board telegraph service. (U.S. Patent 465,971, Means for Transmitting Signals Electrically, 1891).
The most successful creator of an electromagnetic induction system was William Preece in Great Britain. Beginning with tests across the Bristol Channel in 1892, Preece was able to telegraph across gaps of about 5 kilometers. However, his induction system required extensive lengths of wire, many kilometers long, at both the sending and receiving ends, which made it impractical for use on ships or small islands, and the relatively short distances spanned meant it had few advantages over underwater cables.
Electrostatic Induction and Electromagnetic Induction
Heinrich Hertz demonstrated the existence of electromagnetic radiation (radio waves) in a series of groundbreaking experiments in Germany during the 1880s. This led to work in using radio signals for wireless communication, initially with limited success. Using spark-gap transmitters plus coherer-receivers were tried by many experimenters, but several were unable to achieve transmission ranges of more than a few hundred metres. This was not the case for all researchers in the field of the wireless arts, though. By 1897, Guglielmo Marconi conducted a series of demonstrations with an economical radio system for signalling for communications over practical distances. This helped popularize radio communication activity worldwide, which is covered in depth by Invention of Radio and History of Radio.
By the 1920s, there was a worldwide network of commercial and government radiotelegraphic stations, plus extensive use of radiotelegraphy by ships for both commercial purposes and passenger messages. The ultimate implementation of wireless telegraphy was telex using radio signals, which was developed in the 1940s, and was for many years the only reliable form of communication between many distant countries. The most advanced standard, CCITT R.44, automated both routing and encoding of messages by short wave transmissions. (See telegraphy for more information).
John Joseph Fahie, A History of Wireless Telegraphy, 1838-1899: including some bare-wire proposals for subaqueous telegraphs, 1899 (first edition).
John Joseph Fahie, A History of Wireless Telegraphy: including some bare-wire proposals for subaqueous telegraphs, 1901 (second edition).
John Joseph Fahie, A History of Wireless Telegraphy: including some bare-wire proposals for subaqueous telegraphs, 1901 (second edition, in HTML format).
James Bowman Lindsay A short biography on his efforts on electric lamps and telegraphy.
Sparks Telegraph Key Review
Posted by qukjhmhnbfv07 at 7:16 AM