Question

name two differences in Chappe's and mMorse's inventions

Answer 1

Claude Chappe d'Auteroche was born in Brulon, France, in 1763. Claude Chappe initially planned on a career as a member of the clergy, but the French Revolution changed his projects. He then concentrated on scientific work, including long-distance transmission of messages. Most of his work was done with his brothers. They soon rediscovered that complicated messages could be sent using combinations of simple signals. In 1791 a first version of an optical semaphore was devised and successfully used. However, a few more years will be needed to improve the semaphore design and the coding procedure, while efforts were made by the brothers to gain support from the new authorities. In 1794 Claude Chappe was finally put on a government salary. At this stage it is worth remembering that the word telegraph (telegraph, n.- means of sending messages; v.- send a message) comes from French telegraphe. At first, Claude Chappe wanted to call his invention tachygraphe from the Greek for "fast writer", but he was counselled to decide in favour of télégraphe. Claude Chappe committed suicide in 1805, at a time his invention was already a success, to avoid "life's worries" such as criticism and claims from other inventors and competitors. After his death, his brothers Abraham, Ignace and Pierre will be commissioned to organize and chair the telegraph administration.

After early designs using synchronized clocks, and a failed trial to use electricity as a medium for transmission (because no efficient insulator could be found for the electric wires), Chappe devised a semaphore. Preliminary experiments, conducted in 1792, made Claude Chappe and his three brothers convinced that linear arms were more visible in a distance than a shutter semaphore like the one Abraham Edelcrantz was about to built in Sweden in 1794. Therefore, the final design consisted of a long (4 m x 30 cm) rotating bar (the regulator) with two smaller rotating arms (the indicators) on its ends, counterbalanced with metallic weights. While the regulator could be oriented horizontally, obliquely or vertically, the indicators could be independently oriented in one of seven positions 45 degrees apart, giving a total of 98 combinations. Regulator and indicators were black painted to increase contrast against the sky. Abraham-Louis Breguet, a famous clock maker, designed and built a control mechanism allowing an operator, using a scaled-down model of the semaphore to remotely align the full-scaled one from the inside of a building, using pulleys and ropes. The figure on the right shows an example of semaphore design. It is reproduced from. The identical positions of the semaphore and of the scaled-down model are visible.

It was soon discovered that it was impossible to transmit without using control signals and an efficient coding procedure, because errors were inevitable in the process of transmission. After 1795 and a first use of a signalling code which appeared to need improvements, transmissions were done by using 92 combinations of the regulator and indicators. In brief, the regulator could be positioned only vertically or horizontally, and the regulators could be set at angles in increments of 45 degrees, excluding the position where an indicator was extending the regulator. This gave 7 x 7 x 2 = 98 positions, reduced to 92 signals by reserving six signals for special indications. The 92 positions were used to identify in one step a first set (division) of 92 symbols (the alphabet, numbers from zero to nine, some frequently used syllables), or in two steps, first the page number of another 92 page code book (also called a division), and then one symbol (syllables, words, phrases) among the 92 symbols listed on each page. 92 pages time 92 numbered signs, or 8464, means 8464 signs to be transmitted by positioning the semaphore arms twice, transmitting a code pair. After 1799 extra divisions were added giving a total of five. The above six signals reserved for special applications were used to identify the division. The purpose of this system was to save time, by using as few semaphore positions (or symbols) possible to transmit information. It would correspond today to source coding. Basically the formation of a signal was done in two steps and three movements (the French expression "en deux temps et trois mouvements" still meaning today "rapidly done" comes from it). A signal was meaningless as long as the regulator was oblique (left or right), first with the indicators folded in, and then turned to their position (first step consisting of two movements). The left oblique was used for message signals (today the payload) and the right oblique for control signals (today the overhead). The operator had then to verify that the next station was correctly reproducing the signal (corresponding today to restoration at the bit level). This was considered as one of the most important rule to which the operators had to conform. The same error checking was to be made after the second step below. The regulator was then turned to an horizontal or vertical position (second step and third movement). Two examples (from a code table preserved at the Postal Museum in Paris and reproduced in) of the formation of control signals are given in the next table. Each received signal had to be recorded in a book. Additionally, time (hour and minute) was to be recorded for control signals.

The first news transmitted by Chappe telegraph was the victory of French troops at Quesnoy (1794); the last one is supposed to be that of another victory, the fall of Sebastopol (1855). Indeed, during the Crimea war, the mobility of specially designed Chappe semaphores was very appreciated: a station was built in 20 minutes, much faster than long distance electric telegraph lines which were also used for more permanent links during that war. Claude Chappe telegraph was in use for 61 years. It has been the first and largest network using optical telegraph, in continuous operation over more than sixty years. However, the success of the optical telegraph was limited because it was difficult, and therefore expensive, to run, limited to government use, ignored by most of the public, unable to operate at night, vulnerable to fog, mist, and operator misbehaviour, and above all less efficient than the electric telegraph. Nevertheless, optical telegraphs had proven that simple signs could be used to send complex messages, therefore paving the way for electrical communication means. In France, the decision was made in 1846 to replace the optical telegraph by the electric one (installed between Paris and Lille). As a comparison, the first installation of an electric telegraph was done in 1837 in England. The superiority of novel methods, such as the electric telegraph, is often difficult to establish. In this case, the new telegraph needed a physical connection between stations that appeared to be a drawback considering sabotage, and France was reluctant to abandon the old technology in the field of which she was leading. Surprisingly, at first, the electric telegraph in France will consist of a small electrically activated replica of Chappe semaphore, the codes being transmitted using electricity! They will be replaced by Morse telegraph in 1855.

Developed in the 1830s and 1840s by Samuel Morse (1791-1872) and other inventors, the telegraph revolutionized long-distance communication. It worked by transmitting electrical signals over a wire laid between stations. In addition to helping invent the telegraph, Samuel Morse developed a code (bearing his name) that assigned a set of dots and dashes to each letter of the English alphabet and allowed for the simple transmission of complex messages across telegraph lines. In 1844, Morse sent his first telegraph message, from Washington, D.C., to Baltimore, Maryland; by 1866, a telegraph line had been laid across the Atlantic Ocean from the U.S. to Europe. Although the telegraph had fallen out of widespread use by the start of the 21st century, replaced by the telephone, fax machine and Internet, it laid the groundwork for the communications revolution that led to those later innovations.

Before the development of the electric telegraph in the 19th century revolutionized how information was transmitted across long distances, ancient civilizations such as those in China, Egypt and Greece used drumbeats or smoke signals to exchange information between far-flung points. However, such methods were limited by the weather and the need for an uninterrupted line of sight between receptor points. These limitations also lessened the effectiveness of the semaphore, a modern precursor to the electric telegraph. Developed in the early 1790s, the semaphore consisted of a series of hilltop stations that each had large movable arms to signal letters and numbers and two telescopes with which to see the other stations. Like ancient smoke signals, the semaphore was susceptible to weather and other factors that hindered visibility. A different method of transmitting information was needed to make regular and reliable long-distance communication workable.

In the early 19th century, two developments in the field of electricity opened the door to the production of the electric telegraph. First, in 1800, the Italian physicist Alessandro Volta (1745-1827) invented the battery, which reliably stored an electric current and allowed the current to be used in a controlled environment. Second, in 1820, the Danish physicist Hans Christian Oersted (1777-1851) demonstrated the connection between electricity and magnetism by deflecting a magnetic needle with an electric current. While scientists and inventors across the world began experimenting with batteries and the principles of electromagnetism to develop some kind of communication system, the credit for inventing the telegraph generally falls to two sets of researchers: Sir William Cooke (1806-79) and Sir Charles Wheatstone (1802-75) in England, and Samuel Morse, Leonard Gale (1800-83) and Alfred Vail (1807-59) in the U.S.

In the 1830s, the British team of Cooke and Wheatstone developed a telegraph system with five magnetic needles that could be pointed around a panel of letters and numbers by using an electric current. Their system was soon being used for railroad signaling in Britain. During this time period, the Massachusetts-born, Yale-educated Morse (who began his career as a painter), worked to develop an electric telegraph of his own. He reportedly had become intrigued with the idea after hearing a conversation about electromagnetism while sailing from Europe to America in the early 1830s, and later learned more about the topic from American physicist Joseph Henry (1797-1878). In collaboration with Gale and Vail, Morse eventually produced a single-circuit telegraph that worked by pushing the operator key down to complete the electric circuit of the battery. This action sent the electric signal across a wire to a receiver at the other end. All the system needed was a key, a battery, wire and a line of poles between stations for the wire and a receiver.

To transmit messages across telegraph wires, in the 1830s Morse and Vail created what came to be known as Morse code. The code assigned letters in the alphabet and numbers a set of dots (short marks) and dashes (long marks) based on the frequency of use; letters used often (such as “E”) got a simple code, while those used infrequently (such as “Q”) got a longer and more complex code. Initially, the code, when transmitted over the telegraph system, was rendered as marks on a piece of paper that the telegraph operator would then translate back into English. Rather quickly, however, it became apparent that the operators were able to hear and understand the code just by listening to the clicking of the receiver, so the paper was replaced by a receiver that created more pronounced beeping sounds.

In 1843, Morse and Vail received funding from the U.S. Congress to set up and test their telegraph system between Washington, D.C., and Baltimore, Maryland. On May 24, 1844, Morse sent Vail the historic first message: “What hath God wrought!” The telegraph system subsequently spread across America and the world, aided by further innovations. Among these improvements was the invention of good insulation for telegraph wires. The man behind this innovation was Ezra Cornell (1807-74), one of the founders of the university in New York that bears his name. Another improvement, by the famed inventor Thomas Alva Edison (1847-1931) in 1874, was the Quadruplex system, which allowed for four messages to be transmitted simultaneously using the same wire.

Use of the telegraph was quickly accepted by people eager for a faster and easier way of sending and receiving information. However, widespread and successful use of the device required a unified system of telegraph stations among which information could be transmitted. The Western Union Telegraphy Company, founded in part by Cornell, was at first only one of many such companies that developed around the new medium during the 1850s. By 1861, however, Western Union had laid the first transcontinental telegraph line, making it the first nationwide telegraph company. Telegraph systems spread across the world, as well. Extensive systems appeared across Europe by the later part of the 19th century, and by 1866 the first permanent telegraph cable had been successfully laid across the Atlantic Ocean; there were 40 such telegraph lines across the Atlantic by 1940.

The electric telegraph transformed how wars were fought and won and how journalists and newspapers conducted business. Rather than taking weeks to be delivered by horse-and-carriage mail carts, pieces of news could be exchanged between telegraph stations almost instantly. The telegraph also had a profound economic effect, allowing money to be “wired” across great distances.

Even by the end of the 19th century, however, new technologies began to emerge, many of them based on the same principles first developed for the telegraph system. In time, these new technologies would overshadow the telegraph, which would fall out of regular widespread usage. Although the telegraph has since been replaced by the even more convenient telephone, fax machine and Internet, its invention stands as a turning point in world history.