weak current

Electrical telegraph

The electrical telegraph is a telegraph that uses electric signals. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages over wire.


Early works and messages

Electrical phenomena were known from the early history of investigation of electricity to travel with great speed, and many experimenters worked on the problem of applying electricity to communications. All the known effects of electricity - such as sparks, electrostatic attraction, chemical changes, electric shocks, and (later) electromagnetic effects - were applied by various people to the problem of detecting controlled transmission of electricity at a distance.

In 1746 the French scientist and abbé Jean-Antoine Nollet gathered about two hundred monks into a circle about a mile (1.6 km) in circumference, with pieces of iron wire connecting them and discharged a battery of Leyden jars through them; he observed that each man reacted at substantially the same time to the electric shock, showing the speed of propagation to be very high. In 1753 an anonymous writer in the Scots Magazine suggested an electrostatic telegraph, with one wire for each letter of the alphabet - a message could be transmitted by connecting wires in turn to an electrostatic machine, and observing the deflection of pith balls at the far end. While this scheme was eventually demonstrated experimentally in Europe, it was never developed into a useful communication system.

Alessandro Volta invented the Voltaic Pile in 1800, allowing a continuous current for experimentation; this was a source of low-voltage current that could be used to produce different effects than the momentary discharge of electrostatic machines which were the only source of electricity previously known. Samuel Thomas von Soemmering constructed his electrochemical telegraph in 1809. Hans Christian Ørsted discovered in 1820 that an electric current produces a magnetic field which will deflect a compass needle. Also in 1820, Johann Schweigger invented the galvanometer, with a coil of wire around a compass, which could be used as a sensitive indicator for electric current. In 1821, André-Marie Ampère suggested that telegraphy could be done by a system of galvanometers, with one wire per galvanometer to indicate each letter, and said he had experimented successfully with such a system. In 1824, Peter Barlow said that such a system only worked to a distance of about , and so was impractical. William Sturgeon in 1825 invented the electromagnet, with a single winding of uninsulated wire on a piece of varnished iron, which increased the magnetic force produced by electric current. In 1828, Joseph Henry improved the electromagnet by placing on it several windings of insulated wire, creating a much more powerful electromagnet which could operate a telegraph through the high resistance of long telegraph wires. An electromagnetic telegraph was created by Baron Schilling in 1832. Carl Friedrich Gauss and Wilhelm Weber built an electromagnetic telegraph in 1833 in Göttingen. In 1835 Joseph Henry invented the relay, by which a weak current over long wires could operate a powerful local electromagnet.

Gauss-Weber telegraph and Carl Steinheil

Carl Friedrich Gauss, one of the most influential mathematicians of the early 19th century, developed a new theory of the Earth's magnetism in 1831, together with the physics professor Wilhelm Weber in Göttingen. Among the most important inventions of the time was the unifilar and bifilar magnetometer, enabling them to measure even the smallest deflections of the needle. They installed a 1000 m long wire above the town's roofs, which they were given permission for on 6 May 1833. Gauss combined the Poggendorff-Schweigger multiplicator with his magnetometer to build a more sensitive device, the galvanometer. To change the direction of the electric current, he constructed a commutator of his own. As a result, he was able to make the distant needle move in the direction set by the commutator on the other end of the line. At first, they used the telegraph to coordinate time, but soon they developed other signals; finally, their own alphabet. It was not binary, but based on four amplitudes of the needle. Gauss was convinced that this communication would be a help to his kingdom's towns.

Later the same year, instead of a Voltaic pile, Gauss used an induction pulse, enabling him to transmit seven letters a minute instead of two. The inventors and university were too poor to develop the telegraph on their own, but received funding from Alexander von Humboldt. Carl August Steinheil in Munich was able to build a telegraph network within the city in 1835-6, and installed a telegraph line along the first German railroad in 1835.

Schilling telegraph

The telegraph invented by Baron Schilling von Canstatt in 1832 had a transmitting device which consisted of a keyboard with 16 black-and-white keys. These served for switching the electric current. The receiving instrument consisted of 6 galvanometers with magnetic needles, suspended from the silk threads. Both stations of Shilling's telegraph were connected by eight wires; six were connected with the galvanometers, one served for the return current and one - for a signal bell. When at the starting station the operator pressed a key, the corresponding pointer was deflected at the receiving station. Different positions of black and white flags on different disks gave combinations which corresponded to the letters or numbers. Later Pavel Shilling improved its apparatus. He reduced the number of connecting wires from 8 to 2.

On October 21, 1832, Schilling managed a short-distance transmission of signals between two telegraphs in different rooms of his apartment. In 1836 the Schilling's telegraph was tested on a 5 km experimental underground - underwater cable, laid around the building of the main Admiralty in Saint Petersburg. Schilling also was one of the first to put into practice the idea of the binary system of signal transmission.

William Fothergill Cooke studied anatomy in Heidelberg in 1834-6 , where the physics professor introduced him to the Schilling telegraph in 1836.

Alter and the Elderton Telegraph

Across the Atlantic 1836, an American scientist, Dr. David Alter, invented the first known American electric telegraph in Elderton, Pennsylvania, one year before the much more popular Morse telegraph was invented. David demonstrated it to witnesses. He was interviewed later for the book, Biographical and Historical Cyclopedia of Indiana and Armstrong Counties and said: "I may say that there is no connection at all between the telegraph of Morse and others and that of myself...Professor Morse most probably never heard of me or my Elderton telegraph."


The first commercial electrical telegraph was constructed by Sir William Fothergill Cooke. Cooke and Charles Wheatstone patented it in May 1837 as an alarm system. It was first successfully demonstrated by Cooke and Wheatstone on 25 July 1837 between Euston and Camden Town in London. It entered commercial use on the Great Western Railway over the from Paddington station to West Drayton on April 9, 1839. In early 1845, John Tawell was apprehended following the use of a needle telegraph message from Slough to Paddington on January 1 1845. This is thought to be the first use of the telegraph to catch a murderer. The message was:
A murder has just been committed at Salt Hill and the suspected murderer was seen to take a first class ticket to London by the train that left Slough at 7.42pm. He is in the garb of a Kwaker with a brown great coat on which reaches his feet. He is in the last compartment of the second first-class carriage
The reason for the misspelling of 'Quaker' was that the British system did not support the letter Q.

Morse telegraphs

In the United States, the telegraph was developed by Samuel Morse and Alfred Vail. Samuel F. B. Morse independently developed an electrical telegraph in 1837, an alternative design that was capable of transmitting over long distances using poor quality wire. His assistant, Alfred Vail developed the Morse code signalling alphabet with Morse. The Morse code alphabet commonly used on the device was also named after Morse.

On January 6, 1838 Morse first successfully tested the device at the Speedwell Ironworks near Morristown, New Jersey, and on February 8 he publicly demonstrated it to a scientific committee at the Franklin Institute in Philadelphia, Pennsylvania.

In 1843 the U.S. Congress appropriated $30,000 to fund an experimental telegraph line from Washington D.C. to Baltimore. By May 1, 1844 the line had been completed from the U.S. Capitol to Annapolis Junction in Maryland. That day the Whig Party nominated Henry Clay at its national convention in Baltimore. News of the nomination was hand carried by railroad to Annapolis Junction where Vail wired it to Morse in the Capitol. On May 24, 1844, after the line was completed, Morse made the first public demonstration of his telegraph by sending a message from the Supreme Court Chamber in the U.S. Capitol in Washington, D.C. to the B&O Railroad "outer depot" (now the B&O Railroad Museum) in Baltimore. The famous message was: What hath God wrought (from the Biblical book of Numbers 23:23: Surely there is no enchantment against Jacob, neither is there any divination against Israel: according to this time it shall be said of Jacob and of Israel, What hath God wrought!).

The Morse/Vail telegraph was quickly deployed in the following two decades. Morse failed to properly credit Vail for the powerful electromagnets used in his telegraph. The original Morse design, without the relay or the "intensity" and "quantity" electromagnets invented by Vail only worked to a distance of .

This was a practical electrical telegraph system, and subsequently electrical telegraph came to refer to a signaling telegram - a system where an operator makes and breaks an electrical contact with a telegraph key which results in an audible signal at the other end produced by a telegraph sounder which is interpreted and transcribed by a human. Morse and Vail's first telegraphs used a pen and paper system to record the marks of the Morse Code, and interpreted the marks visually however, operators soon realized that they could "read" the clicking of the receiver directly by ear. Systems which automatically read the signals and print formed characters are generally called teletype rather than telegraph systems. Some electrical telegraphs used indicators which were read visually rather than by ear. The most notable of these was the early transatlantic telegraph cable.

According to a Pennsylvania Historical and Museum Commission heritage marker installed along Pennsylvania Route 230 near Elizabethtown, Pennsylvania in 1947 (see image at right), the first commercial telegraph line in the United States ran along a railroad right-of-way (currently part of Amtrak's Keystone Corridor) between Lancaster, Pennsylvania and Harrisburg, Pennsylvania in 1845. The first message, received on January 8, 1846, was "Why don't you write, you rascals?

On October 24, 1861, the first transcontinental telegraph system was established. Spanning North America, an existing network in the eastern United States was connected to the small network in California by a link between Omaha and Carson City via Salt Lake City. The slower Pony Express system ceased operation two days later. Carson City has another claim in the history of telegraphs for the largest and costliest transmission ever sent came from there. Union sympathizers in the American Civil War were eager to gain statehood for Nevada before the next presidential election so that Abraham Lincoln would have enough votes to win. They rushed to send the entire state constitution by telegraph to the United States Congress, which approved it and sent it to the President for signature. They did not believe sending it by train would guarantee it would arrive on time. The constitution was sent on October 31st, just 8 days before the election on November 7th, 1864.

Transatlantic era

The first successful transatlantic telegraph cable was completed on July 27, 1866, allowing transatlantic telegraph communications for the first time. Earlier submarine transatlantic cables installed in 1857 and 1858 only operated for a few days or weeks before they failed. The study of underwater telegraph cables accelerated interest in mathematical analysis of these transmission lines.

In 1867, David Brooks (while working for the Central Pacific Railroad) was awarded and for his improvements to telegraph insulators. He was also awarded reissue number 2,717 in 1867, for , which was originally awarded to him on 1864, for his insulator design. Brooks' patents allowed the Central Pacific to more easily communicate with construction crews building the First Transcontinental Railroad in America; the completion of the railroad was broadcast by telegraph on May 10, 1869, with the telegrapher striking his key in unison with the strikes on the Golden Spike during the completion ceremony.

Another advancement in telegraph technology occurred on August 9, 1892, when Thomas Edison received a patent for a two-way telegraph ("Duplex Telegraph") . On January 27, 2006, Western Union discontinued all telegram and commercial messaging services, though it still offered its money transfer services.

Global communication

Within 29 years of its first installation at Euston Station, the telegraph network crossed the oceans to every continent, making instant global communication possible for the first time. Its development allowed newspapers to cover significant world events in near real-time, revolutionized business, particularly trading businesses, and allowed huge fortunes to be won and lost in a flurry of investment in research and infrastructure building later echoed in the 1990s dot-com bubble.

See also


  • Biographical and Historical Cyclopedia of Indiana and Armstrong Counties, by Wiley, Samuel T., editor, John M. Gresham and Co., Philadelphia PA, 1891, pages 475-476.
  • W.F. Cooke, The Electric Telegraph, Was it invented by Prof. Wheatstone?, London 1856.
  • C.A. Steinheil, Ueber Telegraphie, München 1838.
  • C.F. Gauß, Works, Göttingen 1863-1933.

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