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Alexander Graham Bell (1847-1922) and James Clerk Maxwell (1831-79) were both born in Edinburgh, Scotland. They were probably the two most important Edin-burghers of all-time, others include:
1
Adam Smith, 1723-90. Economist.
2
Sir Arthur Conan Doyle, 1859-1930. Writer.
3
David Hume, 1711-76. Philosopher.
4
Sir Walter Scott, 1771-1832. Writer.
5
Sean Connery, 1930-. Actor.
6
James Boswell, 1740-95. Writer.
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John Knox, 1505-72. Theologian.
8
Muriel Spark, 1918-. Writer.
9
Robert Adam, 1728-92. Architect.
10
Robert Louis Stevenson, 1850-94. Writer.
Other notable mentions:
Elsie Inglis, 1864-1917. Medical pioneer.
Sir Harry Lauder, 1870-1950. Entertainer.

 


 


 

 

 

 

 

 

 

ommunication has always been important to mankind, and a lack of communication in the past has resulted in terrible wars and tragedies. It could be said that the reason that we have had world peace for so long is more to do with global communications, than it has to do with diplomacy.

The Greek philosopher Thales appears to have been the first to document the observations of electrical force. For this he noted that on rubbing a piece of amber with fur caused it to attracted feathers. It is interesting that the Greek name for amber was elektron and the name has since been used in electrical engineering.

An important concept in electrical systems is that electrical energy is undoubtedly tied to magnetic energy. Thus when there is an electric force, there is an associated magnetic force. The growth in understanding of electrics and magnetics began during the 1600s when the court physician of Queen Elizabeth I, William Gilbert, investigated magnets and found that the Earth had a magnetic field. From this he found that a freely suspended magnetic tends to align itself with the magnetic field lines of the Earth. From then on, travelers around the world could easily plot their course because they knew which way was North.

Much of the early research in magnetics and electrics was conducted in the Old World, mainly in England, France and Germany. However, in 1752, Benjamin Franklin put the USA on the scientific map when he flew a kite in an electrical storm and discovered the flow of electrical current. This experiment is not recommended and resulted in the untimely deaths of several scientists.

In 1785, the French scientist Charles Coulomb showed that the force of attraction and repulsion of electrical charges varied inversely with the square of the distance between them. He also went on to show that two similar charges repel each other, while two dissimilar charges attract.

Two scientists who would be commemorated by electrical units made must of there major findings in the 1820s. The French scientist André Ampère was studying electrical current in wires and the forces between them, and then, in 1827, the German scientist Georg Ohm studied the resistance to electrical flow. From this, he determined that resistance in a conductor was equal to the voltage across the material divided by current through it. Soon after this, English scientist Michael Faraday produced an electric generator when he found that the motion of a wire through an electric field generated electricity. From this, he mathematically expressed the link between magnetism and electricity.

The root of modern communication can be traced back to the work of Henry, Maxwell, Hertz, Bell, Marconi and Watt. American Joseph Henry produced the first electromagnet when he wrapped a coil of insulated electrical wire around a metal inner. Henry, un-fortunately, like many other great scientists, did not patent his discovery. If he had he would have enjoyed his retirement years as a very wealthy man, rather than on his poor pension. The first application of the electromagnet was in telegraphy, which was the beginning of the communications industry. Henry sent coded electrical pulses over telegraph wires to an electromagnet at the other end. It was a great success, but it was left to the artist Samuel Morse (the American Leonardo, according to one of his biographers) to take much of the credit. Morse, of-course developed Morse Code, which is a code of dots and dashes. He used Henry's system and installed it in a telegraph system from Washington to Baltimore. The first transmitted message was "What hath God wrought." It received excellent publicity and after eight years there were over 23000miles (37000km) of telegraph wires in the USA. Several of the first companies to develop telegraph systems went on to become very large corporations, such as the Mississippi Valley Printing Telegraph Company which later be-came the Western Union. One of the first non-commercial uses of telegraph was in the Crimean War and the American Civil War, where a communications line from New York to San Francisco was an important mechanism for transmitting information to and from troops.

Other important developers of telegraph systems around the world were P.L. Shilling in Russia, Gauss and Weber in Germany, and Cooke and Wheatstone in Britain. In 1839 Cooke and Wheatstone opened telegraph system alongside the main railway route running west from London.

One of the all time greats was the James Clerk Maxwell, who was born in Edinburgh in 1831. He rates amongst the greatest of all the human beings who have walked on this planet and his importance to science puts him on par with Isaac Newton, Albert Einstein, James Watt and Michael Faraday. Maxwell's most famous formulation was a set of four equations that define the basic laws of electricity and magnetism (Maxwell's equations). Before Maxwell's work, many scientists had observed the relationship between electricity and magnetism. However, it was Maxwell, who finally derived the mathematical link between these forces. His four short equations described exactly the behavior and interaction of electric and magnetic fields. From this work, he also proved that all electromagnetic waves, in a vacuum, travel at 300000 km per second (or 186000 miles per second). This, Maxwell recognized, was equal to the speed of light and from this, he deduced that light was also an electromagnetic wave. He then reasoned that the electromagnetic wave spectrum must contain many invisible waves, each with its own wavelength and characteristic. Other practical scientists, such as Hertz and Marconi soon discovered these 'unseen' waves. The electromagnetic spectrum was soon filled with infrared waves, ultraviolet, gamma ray, X-rays and radio waves (and some even proposed waves which did not even exist).

Maxwell is probably the second greatest scientist ever (Isaac Newton would obviously be in first place). Maxwell's four equations which define the propagation of every electromagnetic wave:

 

 

 

 

 

 

 

While Maxwell would provide a foundation for the transmission of electrical signals, another Scot, Alexander Graham Bell, would provide a mechanism for the transmission and reception of sound: the telephone. From his time in Scotland he has always had a great in-terest in the study of speech and elocution. In the USA, he fully developed his interest and opened the Boston School for the Deaf. His other interest was in multiple telegraphy and he worked on a device which he called a harmonic telegraph, which he used to aid the teaching of speech to deaf people. In 1876, out of this research he produced the first telephone with an electromagnet for the mouthpiece and the receiver. Alexander Graham Bell actually made the telephone call to his assistant with the words "Mr Watson, come here, I want you". Unlike many other great inventions it got good press coverage. "It talks" was one of the headline (it has not stopped since). Even the great Maxwell was even amazed that anything so simple could reproduce the human voice and, in 1877, Queen Victoria acquired a telephone. Edison then enhanced it by using carbon powder in the diaphragm, to create a basic microphone. This produced an increased amount of electrical current. To fully commercial-ize his invention, Bell along with several others formed the Bell Telephone Company which fully developed the telephone so that, by 1915, long-distance telephone calls were possible. Bell's patent number 174465 is the most lucrative ever issued. At the time, a reporter wrote, about the telephone, "It is an interesting toy . but it can never be of any practical value."

Around 1851, the brothers Jacob and John Watkins Brett laid a cable across the English Channel between Dover and Cape Griz Nez. It was the first use of electrical communica-tions between England and France (unfortunately a French fisherman mistook it for a sea monster and trawled it up). The British maintained a monopoly on submarine cables and laid cables across the Thames, Scotland to Ireland, England to Holland, as well as cables under the Black Sea, the Mississippi River and the Gulf of St Lawrence. Submarine cables have since been placed under most of the major seas and oceans around the world.

Around 1888, German Heinrich Hertz detected radio waves (as predicted by Maxwell) when he found that a spark produced an electrical current in a wire on the other side of the room. Then, Guglielmo Marconi, in 1896, succeeded in transmitting radio waves over a dis-tance of two miles. From this humble start, he soon managed to transmit a radio wave across the Atlantic Ocean.

Scot Robert Watson-Watt made RADAR (radio detection and ranging) practicable in 1935, by transmitting microwave electromagnetic pulses which where reflected by metal objects (normally planes or ships) and were detected by a receiver. Today it is used in many applications from detect missiles and planes, to detecting rain clouds and detecting the speed of motor cars. Microwave signals have been important in the development of satellite communications.


History of modern communications

The main developments of modern communications have been:

Automated telephone switching. After the telephone's initial development, call switching was achieved by using operators. This tended to limit the range of the calls, and was particularly unreliable (and not very secure, as operators would often listen to the tele-phone conversation). However, in 1889, Almon Strowger, a Kansas City undertaker, patented an automatic switching system. In one of the least catchy advertising slogans, it was advertised as "a girl-less, cuss-less, out-of-orderless, wait-less telephone system". His motivation for the invention was to prevent his calls being diverted to a business competitor by his local operator. It used a pawl-and-ratchet system to move a wiper over a set of electrical contacts. This led to the development of the Strowger exchange, which was used extensively until the 1970s. Another important improvement came with the crossbar, which allowed many inputs to connect to many outputs, simply by ad-dressing the required connection. The first inventor is claimed to be J.N Reynolds of Bell Systems, but it is normally given to G.A. Betulander.

Radio transmission. One of the few benefits of war (whether it be a real war or a cold war) is the rapid development of science and technology. Radio transmission benefited from this over World War I. A by-product of this work was frequency modulation (FM) and amplitude modulation (AM). In these, signals to be carried on (modulated) high frequency carrier waves which traveled through the air better than unmodulated waves. Another by-product of the war effort was frequency division multiplexing (FDM) which allowed many signals to be transmitted over the same channel, but with a different car-rier frequency.

Trans-continental cables. After the Second World War, the first telephone cable across the Atlantic was laid from Oban, in Scotland to Clarenville in Newfoundland. Previ-ously, in 1902, the first Pacific Ocean cable was laid. A cable, laid in 1963, stretches from Australia to Canada. These trans-continental cables are now important trunk routes for the global Internet. Their capacity has increased over the years, especially with the in-troduction of fiber optic cables.

Satellites. The first artificial satellite was Sputnik 1, which was launched by the USSR in 1957. This was closed followed in the following year by the US satellite, Explorer 1. The great revolution can when the ATT-owned Telstar satellite started communicating over large distances using microwave signals. It used microwave signals which could propa-gate through rain and clouds and bounce off the satellite. The amount of information that can be transmitted varies with the bandwidth of the system, and is normally lim-ited by the transmission system. A satellite system can carry as much as 10 times the amount of information that a radio wave can carry. This allows several TV channels to be transmitted simultaneously and/or thousands of telephone calls. Satellite TV sta-tions have been popular in transmitting TV stations over large areas.

Digital transmission and coding. Most information transmitted is now transmitted in the form of digital pulses. A standard code for this transmission, called Pulse code modulation (PCM), was invented by A.H. Reeves in the 1930s, but not used until the 1960s. A major problem in the past with computers systems was that they used different codes to transmit text. To overcome this Baudot developed a 5-unit standard code for telegraph systems. Unfortunately, it had a limited alphabet of upper-case letters and had only a few punctuation symbols. In 1966, ANSI defined a new standard code called ASCII. This has since become the standard coding system for text-based communica-tions. It has only recently been upgraded with Unicode (which uses 16 bits). In its standard form it uses 7 bits and can thus only represent up to 128 characters. It has since been modified to support an 8-bit code (called Extended ASCII).

Fiber optic transmissions. Satellite communications increased the amount of data that could be transmitted over a channel, but in 1965 Charles Kao laid down the future of high-capacity communication with the proof that data could be carried using optical fibers. Optical fibers now provide the backbone to many networks, including the Inter-net. Satellites supported the transmission of many hundreds of bits per second, but fiber optics could support billions of bits per second over a single fiber. They are reliable, and have excellent capacity for future upgrading with a new transfer rate.

 

Chapter 7, Mastering Computing, W.Buchanan, Palgrave.

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