Definition

telegraph

A telegraph is a communications system in which information is transmitted over a wire through a series of electrical current pulses, usually in the form of Morse code. The basic components include a source of direct current, a length of wire or cable, and a current-indicating device such as a relay, buzzer, or light bulb. The term comes from the Greek words "tele," meaning "at a distance" and "graphien," meaning "to write."

The telegraph has been in use for more than 150 years. The prototype of the telegraph was demonstrated by Joseph Henry in 1830. He transmitted an electric current over a length of wire approximately 1 mile (1.6 kilometer) in length to activate a bell on the opposite end of the circuit. This device was refined and developed by Samuel F. B. Morse into a system that used a solenoid, equipped with a marker, to record multiple pulses of varying duration on a moving strip of paper. These pulses appeared as so-called dots and dashes. Patterns of these dots and dashes were assigned to letters of the alphabet, single-digit numerals, and punctuation marks. On May 1, 1844, the first official telegraph message was sent.

The telegraph was, arguably, one of the two most important technological advances that contributed to U.S. settlement of North America west of the Mississippi River. (The other was the railroad.) The telegraph is still occasionally used for communication, but the Internet and the telephone are employed far more often. A variant of the original Morse code is used by amateur radio operators today, largely for recreation, but occasionally in emergencies when all other modes of communication fail as a result of infrastructure damage or because of poor wave propagation conditions. The amateur radio operator reads the code by listening to audio tones from a radio receiver. The human ear, working in conjunction with the brain, is one of the most sensitive known data interpreters, and the Morse code, because it is binary, remains among the most efficient, albeit slow, data transmission methods.

Western Union, a U.S.-based financial and communications service company, was founded in the 1850s to take advantage of the then new technology. Since then, Western Union conveyed telegrams all over the world. However, as the Internet and e-mail have become increasingly prevalent around the globe, the telegram has been less frequently used and considered more and more anachronistic. In January 2006, Western Union announced -- on the Internet -- that it would no longer be sending telegrams.

This was last updated in March 2008
Posted by: Margaret Rouse

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