Telegraph , any device or system that allows the transmission of information by coded signal over distance Many telegraphic systems have been used over the centuries , but the term is most often understood to refer to the electric telegraph , which was developed in the mid - 19th century and for more than 100 years was the principal means of transmitting printed information by wire or radio wave .
- Pre - electric telegraph systems
The word telegraph is derived from the Greek words tele , meaning “ distant ” and graphein , meaning “ to write ” It came into use toward the end of the 18th century to describe an optical semaphore system developed in France . However , many types of telegraphic communication have been employed since before recorded history . The earliest methods of communication at a distance made use of such media as smoke and fire , drums , and reflected rays of the Sun .
Visual signals given by flags and torches were used for short - range communication and continued to be utilized well into the 20th century , when the two - flag semaphore system was widely used , particularly by the world’s navies.
- The beginning of electric telegraphy : The first transmitters and receivers
The electric telegraph did not burst suddenly upon the scene but rather resulted from a scientific evolution that had been taking place since the 18th century in the field of electricity . One of the key developments was the invention of the voltaic cell in 1800 by Alessandro Volta of Italy . In 1832 Samuel F.B. Morse , a professor of painting and sculpture at the University of the City of New York « later New York University » , became interested in the possibility of electric telegraphy and made sketches of ideas for such a system .
In 1835 he devised a system of dots and dashes to represent letters and numbers . In 1837 he was granted a patent on an electromagnetic telegraph . Morse’s original transmitter incorporated a device called a portarule which employed molded type with built - in dots and dashes . The type could be moved through a mechanism in such a manner that the dots and dashes would make and break the contact between the battery and the wire to the receiver. The receiver , or register , embossed the dots and dashes on an unwinding strip of paper that passed under a stylus . The stylus was actuated by an electromagnet turned on and off by the signals from the transmitter .
Morse had formed a partnership with Alfred Vail , who was a clever mechanic and is credited with many contributions to the Morse system . Among them are the replacement of the portarule transmitter by a simple make - and - break key , the refinement of the Morse Code so that the shortest code sequences were assigned to the most frequently occurring letters and the improvement of the mechanical design of all the system components .
The first demonstration of the system by Morse was conducted for his friends at his workplace in 1837 . In 1843 Morse obtained financial support from the U.S . government to build a demonstration telegraph system 60 km « 35 miles » long between Washington , D.C. , and Baltimore . The system was completed and public use initiated on May 24 , 1844 , with a transmission of the message , “ What hath God wrought ! ” This inaugurated the telegraph era in the United States , which was to last more than 100 years .
Development of the telegraph industry
Although railroad traffic control was one of the earliest applications of the telegraph , it immediately became a vital tool for the transmission of news around the country . In 1848 the Associated Press was formed in the United States to pool telegraph expenses, and in 1849 Paul Julius Reuters in Paris initiated telegraphic press service « using pigeons to cover sections where lines were incomplete » . By 1851 more than 50 telegraph companies were in operation in the United States .
Signal processing and transmission
During this time of rapid change in the telegraph industry a new device , the telephone , was patented by Alexander Graham Bell in 1876 . Although the telephone was originally expected to replace the telegraph completely , this turned out not to be the case : both industries thrived side by side for many decades . Much of the technology developed for telephony had parallel applications in telegraphy . A number of systems were developed that allowed simultaneous transmission of telegraph and telephone signals on the same lines In 1882 the Western Electric Company was acquired from Western Union by the American Bell Telephone Company . Western Electric had started as a telegraph manufacturing company but later became a major contributor to both the telephone and telegraph industries .
E.C.Heasley , Jules A . Rodier , and Major Montgomery working in the White House's Telegraph Room — which was set up to receive news of the Spanish - American War — in Washington , D.C., 1898 . Library of Congress , Washington , D.C. « digital . id . cph . 3b37154 »
In 1903 the British inventor Donald Murray , following the ideas of Baudot , devised a time - division multiplex system for the British Post Office . The transmitter used a typewriter keyboard that punched tape and the receiver printed text . He modified the Baudot Code by assigning code combinations with the fewest punched holes to the most frequently encountered letters and symbols . Murray sold the patent rights to Western Union and Western Electric in 1912 , and this formed the basis of the printing telegraph systems that came into use in the 1920s .
Morse telegraph register from the 1840s . the register received a transmitted signal and transcribed the morse code symbols onto a strip of a paper wound from the spools. smithsonian institution .
In 1924 the American Telephone & Telegraph Company « AT&T » introduced a printing telegraph system called the Teletype, which became widely used for business communication . The unit consisted of a typewriter keyboard and a simplex printer . Each keystroke generated a series of coded electric impulses that were then sent over the transmission line to the receiving system . There the receiver decoded the pulses and printed the message on a paper tape or other medium . In 1932 AT&T inaugurated the Teletypewriter Exchange Service « TWX » , a switched teleprinter network . Switching was accomplished manually until it was automated after World War II . In Europe , a similar service called Telex was inaugurated in the early 1930s and was partially automated in Germany before World War II . In 1962 Western Union introduced Telex in the United States as an international teleprinter service, and in 1970 it acquired TWX from AT&T . It was not possible for the Telex and TWX instruments to communicate directly with one another because of differences in transmission codes and transmission speeds. Western Union linked the two services through a network of processing centers that made the necessary conversions between the two systems .
The End Of The Telegraph Era
After World War II much new technology became available that radically changed the telegraph industry Old wire lines were too expensive to maintain and were replaced by coaxial cable and microwave links . Very wide - bandwidth channels became available , allowing transmission speeds limited only by the capabilities of the terminal equipment . These new transmission media were later augmented by satellite links and fiber optic transmission lines . In 1974 the Westar satellite , providing enormous capacity for all types of telecommunication , was placed in operation by Western Union .
TeleprinterA T100 Telex teleprinter.Flominator
These new transmission channels were complemented by new electronic technology including transistors integrated circuits , and various microelectronics devices that reduced costs and improved performance With the advent of the digital computer in the 1960s the trend toward entirely digital communication began The facsimile telegraph was perfected in the 1930s and was widely used for sending photographs and other graphics information over telephone and telegraph lines in an analog transmission system. By the 1980s however , analog facsimile was virtually replaced by the digital fax machine . In many offices , fax machines and e-mail began to replace other types of communication , including telegrams , TWX , Telex , and in many cases , the postal service . In the face of changing technology , the Western Union Telegraph Company was reorganized as the Western Union Corporation in 1988 to handle money transfers and related services . It sold its international private line service to Tele-Columbus AG of Switzerland , the Westar satellite system was sold to GM Hughes Electronics Corporation of the United States , and AT&T acquired Western Union’s business services group . The Telegraph , which had started in 1837 , was replaced in most applications in developed countries by digital data-transmission systems based on computer technology .