Telegraphy is the long-distance transmission of written messages without physical transport of letters. It is a compound term formed from the Greek words tele (τηλε) = far and graphein (γραφειν) = write. Radiotelegraphy or wireless telegraphy transmits messages using radio.
A telegraph is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. The word telegraph alone now generally refers to an electrical telegraph. Wireless telegraphy is also known as "CW", for continuous wave (a carrier modulated by on-off keying), as opposed to the earlier radio technique of using a spark gap.
A telegraph message sent by an electrical telegraph operator or telegrapher using Morse code (or a printing telegraph operator using plain text) was known as a telegram. A cablegram (see cablegram) was a message sent by a submarine telegraph cable, often shortened to a cable or a wire. Later, a Telex was a message sent by a Telex network, a switched network of teleprinters similar to a telephone network.
Before long distance telephone services were readily available or affordable, telegram services were very popular and the only way to convey information speedily over very long distances. Telegrams were often used to confirm business dealings and were commonly used to create binding legal documents for business dealings.
A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. The teleostereograph machine, a forerunner to the modern electronic fax, was developed by AT&T's Bell Labs in the 1920s; however, the first commercial use of image facsimile telegraph devices date back to the 1800s. It was made by Samuel F. B. Morse (the inventor of morse code).
The first telegraphs came in the form of optical telegraph including the use of smoke signals, beacons or reflected light, which have existed since ancient times. A semaphore network invented by Claude Chappe operated in France from 1792 through 1846. It helped Napoleon enough to be widely imitated in Europe and the U.S. In the Peninsular War (1807-1814), several similars telegraphs had been used in the Lines of Torres Vedras, by the anglo-portuguese army. The Prussian system was put into effect in the 1830s. The last commercial semaphore link ceased operation in Sweden in 1880.
Semaphores were able to convey information more precisely than smoke signals and beacons, and consumed no fuel. Messages could be sent at much greater speed than post riders and could serve entire regions. However, like beacons, smoke and reflected light signals they were highly dependent on good weather and daylight to work (practical electrical lighting was not available until about 1880). They required operators and towers every 30 km (20 mi), and could only accommodate about two words per minute. This was useful to governments, but too expensive for most commercial uses other than commodity price information. Electric telegraphs were to reduce the cost of sending a message thirtyfold compared to semaphores, and could be utilized non-stop, 24 hours per day, independent of the weather or daylight.
Elevated locations where optical telegraphs were placed for maximum visibility were renamed to Telegraph Hill, such as Telegraph Hill, San Francisco, and Telegraph Hill in the PNC Bank Arts Center in New Jersey.
One very early experiment in electrical telegraphy was an electrochemical telegraph created by the German physician, anatomist and inventor Samuel Thomas von Sömmering in 1809, based on an earlier, less robust design of 1804 by Catalan polymath and scientist Francisco Salvá i Campillo. Both their designs employed multiple wires (up to 35) in order to visually represent most Latin letters and numerals. Thus, messages could be conveyed electrically up to a few kilometers (in von Sömmering's design), with each of the telegraph receiver's wires immersed in a separate glass tube of acid. As an electric current was applied by the sender representing each digit of a message, it would at the recipient's end electrolyse the acid in its corresponding tube, releasing a stream of hydrogen bubbles next to its associated letter or numeral. The telegraph receiver's operator would visually observe the bubbles and could then record the transmitted message, albeit at a very low baud rate.
Carl Friedrich Gauss and Wilhelm Weber built and first used for regular communication the electromagnetic telegraph in 1833 in Göttingen, connecting Göttingen Observatory and the Institute of Physics, covering a distance of about 1 km. The setup consisted of a coil which could be moved up and down over the end of two magnetic steel bars. The resulting induction current was transmitted through two wires to the receiver, consisting of a galvanometer. The direction of the current could be reversed by commuting the two wires in a special switch. Therefore, Gauss and Weber chose to encode the alphabet in a binary code, using positive current and negative as the two states.
A replica commissioned by Weber for the 1873 World Fair based on his original designs is on display in the collection of historical instruments in the Department of Physics at University of Göttingen. There are two versions of the first message sent by Gauss and Weber: the more official one is based on a note in Gauss's own handwriting stating that "Wissen vor meinen – Sein vor scheinen" ("knowing before opining, being before seeming") was the first message sent over the electromagnetic telegraph. The more anecdotal version told in Göttingen observatory is that the first message was sent to notify Weber that the observatory's servant was on the way to the institute of physics, and just read "Michelmann kommt" ("Michelmann is on his way"), possibly as a test who would arrive first.
The first commercial electrical telegraph was co-developed by Sir William Fothergill Cooke and Charles Wheatstone, and entered use on the Great Western Railway in Britain. It ran for from Paddington station to West Drayton and came into operation on 9 July 1839. It was patented in the United Kingdom in 1837, and was first successfully demonstrated by Cooke and Wheatstone on 25 July 1837 between Euston and Camden Town in London. In 1843 Scottish inventor Alexander Bain invented a device that could be considered the first facsimile machine. He called his invention a "recording telegraph". Bain's telegraph was able to transmit images by electrical wires. In 1855 an Italian abbot, Giovanni Caselli, also created an electric telegraph that could transmit images. Caselli called his invention "Pantelegraph". Pantelegraph was successfully tested and approved for a telegraph line between Paris and Lyon.