Electricity and Communications

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Blaise Martin
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Electricity is the medium of choice for transporting and transmitting energy from many other sources.

1 Electricity and Communications 1 Electricity Every aspect of modern industrialized world is dependent on a steady supply of electricity. All modern communications equipment runs on electricity, as do all computers. Electricity is the all-purpose form of energy that runs lighting systems and most appliances. Electricity is the medium of choice for transporting and transmitting energy from many other sources. 2 History of Electricity Electricity began to be studied and understood around the beginning of the Industrial Revolution. Benjamin Franklin determined that the two kinds of electric charge known, positive and negative, cancel each other when brought together. They were merely polarities of the same thing. He also established that lightning is electricity, with his famous kite experiment. 3 1

The Electric Battery In 1800, Alessandro Volta found a way to store electricity by making a pile of alternating copper and zinc plates, separated by cardboard

4 Electricity and Magnetism In the 19th century, scientists discovered the link between electricity and magnetism: A changing electric current produces a

That electricity can then be used to cause motion elsewhere.

2 The Electric Battery In 1800, Alessandro Volta found a way to store electricity by making a pile of alternating copper and zinc plates, separated by cardboard soaked in acid. This was the first electric battery. 4 Electricity and Magnetism In the 19th century, scientists discovered the link between electricity and magnetism: A changing electric current produces a magnetic attraction, and a moving magnet produces an electric current. Any form of energy can be used to move (e.g. spin) a magnet, which will make electricity. That electricity can then be used to cause motion elsewhere. 5 Signalling One of the first practical uses of electricity was to improve the technology of long distance communication. Until electricity was used to send messages, communication was limited first by the distance that sound will travel and be recognizable and, given a coding system, by the distance that can be seen and interpreted. At right, a 1792 French semaphore station. 6 2

The Idea of the Telegraph In the 1830s experiments were made in sending signals by turning an electric current on and off on in connecting wires.

7 Morse Code and the Telegraph In the 1840s, Samuel Morse invented a code that represented each letter of the alphabet as a combination of short and

This used a single wire, instead of 5 or more in previous inventions.

3 The Idea of the Telegraph In the 1830s experiments were made in sending signals by turning an electric current on and off on in connecting wires. This produced a magnetic field that would disturb a magnet at the other end of the wire. At right, the Cooke & Wheatstone 5-needle telegraph. 7 Morse Code and the Telegraph In the 1840s, Samuel Morse invented a code that represented each letter of the alphabet as a combination of short and longer signals, which could be represented by turning an electric current on and off quickly again and again. This used a single wire, instead of 5 or more in previous inventions. 8 The Telegraph takes off By 1850 every state of the US east of the Mississippi was on the telegraph network. The main first users were the railroads, that needed timely information about train traffic. Next was commerce. Downtown New York was crisscrossed in no time with telegraph wires on poles. 9 3

10 Speaking on the Telegraph Alexander Graham Bell, a teacher of deaf children, tried to invent a device that would make recognizable electric signals that could be

4 Telegraph lines unite the Industrialized World By 1861, a telegram could be sent across North America, from New York to San Francisco. By 1866 there were already two undersea cables crossing the Atlantic Ocean. 10 Speaking on the Telegraph Alexander Graham Bell, a teacher of deaf children, tried to invent a device that would make recognizable electric signals that could be interpreted by the deaf children. He found a way to convert ordinary sound into electric impulses at varying frequencies and then use the electricity to vibrate a magnet that would emit sound waves. 11 The Telephone Alexander Graham Bell inaugurating the first New York to Chicago telephone line. 12 4

The Telephone Network First used in businesses as a point to point communication device where frequent distance communication was necessary. E.g. into mines, from warehouse to head office.

The picture is of a 19th century switchboard, probably from a large business with phones in different departments and locations.

5 The Telephone Network First used in businesses as a point to point communication device where frequent distance communication was necessary. E.g. into mines, from warehouse to head office. Later, the idea of a network of phone lines that could call any of each other developed. These required a central exchange. The picture is of a 19th century switchboard, probably from a large business with phones in different departments and locations. 13 Making the Telephone a Commodity Like many technological facets of modern society that provided a new range of services, the first customers were those who immediately perceived the telephone s value for their current needs. It inevitably took longer for a wider public to be convinced that the new gadget was something they would view as a necessity once they had it. This required advertising. The telephone was one of the first modern-day inventions that was promoted with display ads in newspapers and magazines by the Bell Telephone company. 14 An Ad for the Bell Telephone of

6 The Telegraph blazes the trail for the Telephone The telephone had its first successes where the telegraph was already well established, namely the United States and Canada. The telegraph lines were already in heavy use to compensate for the relatively long distances between cities and towns in North America, and because of the prominence of the railroads. The telegraph lines could easily be adapted to telephone usage. (Of course, Bell was from Canada and the United States.) 16 The Spread of Telephones In the industrialized nations, the telephone spread quickly. In the U.S., The number of telephones doubled every four years between 1880 and 1900, from 48,000 to 1,350,000. In Europe, the pace was slower, perhaps because, unlike North America, the phone service was run by the post offices. In 1911, the ratio of telephones to people in the US was 1 to 20. In Britain and Germany, it was 1 to 100. Elsewhere it was much lower. 17 Telephones Everywhere Telephones are now universal in the industrialized nations. In countries that never did get universal landline service, cell phones have an even greater rate of growth than in some industrialized nations. Instead of laying down the expensive infrastructure of land lines, these countries have put their capital into wireless transmitters. 18 6

7 Modern society impossible without the telephone? A quote from Robert Bruce s biography of Alexander Graham Bell: Without the telephone as its nervous system, the twentieth-century metropolis would have been stunted by congestion and slowed to the primordial pace of messengers and postmen. And the modern industrial age would have been born with cerebral palsy. 19 Electric Lighting Like the bicycle preceding the automobile and the telegraph preceding the telephone, each created a demand for a service that was provided better by the following technology. For artificial lighting, the oil lamp created a demand for night lighting, that gas lighting built upon. If electricity could be used to make a better light, there was a ready market to exploit. Enter the inventor. 20 Thomas Alva Edison One of the world s first professional inventors. Lodged 1093 patents. Edison created many gadgets that used the power of electricity: The phonograph. The motion-picture camera. The stock ticker. The repeating telegraph. Edison began the practice of answering the phone with hello. 21 7

The electric light bulb Electricity, forced through a poor conductor, gives off a glow. It also produces heat, generally enough to set the glowing object on fire.

Edison placed a filament a poor electrical conductor inside a container emptied of air, and forced electricity through it.

Edison organized an extravagant display of the potential of electric street lighting in his home town of Menlo Park, New Jersey on December 31, 1879, attended by dignitaries brought in by a

8 The electric light bulb Electricity, forced through a poor conductor, gives off a glow. It also produces heat, generally enough to set the glowing object on fire. But if the electrified object has no oxygen around it, it cannot burn, and therefore will just continue to glow. Edison placed a filament a poor electrical conductor inside a container emptied of air, and forced electricity through it. After many unsuccessful attempts, he and his helpers found a combination that worked. 22 Street lighting by electricity Gas and oil street lights were already common. Edison organized an extravagant display of the potential of electric street lighting in his home town of Menlo Park, New Jersey on December 31, 1879, attended by dignitaries brought in by a special train. It worked, and it did not take long before there was a steady demand for electric lighting. 23 Electric power everywhere Edison realized that to sell his invention of the light bulb, there had to be a supply of electricity readily available. So he also developed the concept of the electric power generating station, and the beginning of the power grid that crisscrosses all industrialized communities. 24 8

9 Wireless Communications Both the telegraph and the telephone carried messages at the speed of light, but only through connected metal wires. This meant that communication was limited to fixed locations. Ships at sea were still cut off from electrical communication technology. They remained limited to communication by direct line of sight and semaphores or flashing lights. 25 Guglielmo Marconi Guglielmo Marconi, a young inventive Italian with a wealthy British mother, figured out how to use electromagnetic waves to send controlled disturbances through space that could be read by a receiving device not connected to the sending device. 26 Finding the market He realized that this could be the basis of a wireless electric communication device, which had tremendous potential. Marconi failed to get the Italian government interested in his invention, but he figured that Britain, the world s greatest shipping and naval power would see the benefit of a device that could communicate with ships at sea. 27 9

The Wireless Telegraph and Signal Company He and his British mother moved to Britain in the late 19th century, and formed the Wireless Telegraph and Signal Company.

The Marconi device sent sparks using Morse code that was deciphered the same as on land telegraph lines.

In 1901, Marconi had attempted to transmit a wireless message from Cornwall, in the southwest of England to Signal Hill in St. John s, Newfoundland.

10 The Wireless Telegraph and Signal Company He and his British mother moved to Britain in the late 19th century, and formed the Wireless Telegraph and Signal Company. In five years, there were 25 shore stations and 70 ships equipped with transmitting and receiving equipment. The Marconi device sent sparks using Morse code that was deciphered the same as on land telegraph lines. 28 Trans-Atlantic Wireless Telegraphy By 1908, every large trans- Atlantic ocean liner carried a Marconi operator and receiving and transmitting equipment. In 1901, Marconi had attempted to transmit a wireless message from Cornwall, in the southwest of England to Signal Hill in St. John s, Newfoundland. It is controversial whether the experiment was a success, but it whet an appetite for longdistance wireless telegraphy. Signal Hill, St. Johns, Newfoundland 29 Vacuum tubes Marconi used radio waves only to carry a slow or a fast spark a dot or a dash in Morse code. Radio waves could carry much more varied information if the frequency of the wave could be altered in complex ways. With the invention of the vacuum tube, a continuous wave transmission was possible

Reginald Fessenden Canadian Reginald Fessenden was the person who figured out how to add modulation to a steady wave that could carry information as complex as human speech.

11 Reginald Fessenden Canadian Reginald Fessenden was the person who figured out how to add modulation to a steady wave that could carry information as complex as human speech. 31 Fessenden s Christmas Surprise Fessenden sprang his discovery of how to send speech and other complex sounds out over radio waves on an unsuspecting audience. On December 24, 1906, Fessenden sent a wireless telegraph message in Morse code to ships at sea off the coast of Massachusetts, telling the wireless operators to be sure to be tuned in at a specific time for an important message to be transmitted then. At the appointed hour, he turned on his modulating equipment and broadcast a program of Christmas greetings and music to the very startled operators. 32 Broadcasting demanded Even with voice transmissions, the emphasis in radio had been point-to-point communication from one station to another. The general idea of broadcast transmissions was not envisaged. Wireless telegraph operators already had the equipment that could receive more complex radio signals, so the technology was already in place. In a few short years, experimental broadcasts to wireless operators became so popular that there was a demand for regular broadcasting

Radio Programs The public began to obtain radio sets of their own, and existing telegraph operators set up radio stations to provide programming in the 1920s. A radio drama, broadcast live.

12 Radio Programs The public began to obtain radio sets of their own, and existing telegraph operators set up radio stations to provide programming in the 1920s. A radio drama, broadcast live. 34 Television Radio is the transmission and reception of modulated electromagnetic waves. There is really nothing different in kind involved in the transmission of pictures as well as sound, only the technical problem of encoding a picture into a transmission and then decoding it back into an image by the receiver. The trick is to divide a picture into tiny squares (pixels) that are either on or off (black or white) and then encode this as an electrical signal that is either on or off. 35 The Baird TV John Baird s television camera. It used a system of rotating discs to divide a picture into a linear series of bits, which would each be represented by an electrical signal. The receiver would undo the signal and reconstruct the image with a similar set of spinning discs

13 The Television Set Early cathode ray picture tubes reassembled the stream of electromagnetic bits onto a small area so quickly that the eye thought it was continuous movement. Original TV broadcasting began in the 1930s, but did not become widely popular until after the Second World War

1 Electricity and Communications. 2 Electricity. 3 History of Electricity. 4 The Electric Battery. 5 Electricity and Magnetism.

1 Electricity and Communications 2 Electricity Every aspect of modern industrialized world is dependent on a steady supply of electricity. All modern communications equipment runs on electricity, as do