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HOW AND WHY NEW! A collector's binder to hold HOW AND WHYL, This new How and Why collector's binder holds twelve titles: a wonderful way to build your own reference library! It is^available from the publishers of How and Why books for £2.00 Supplies are limited so send for yours now.

Transworld Publishers Limited, Cash Sales Dept., P.O. Box 11, Falmouth, Cornwall. Plus 50p Postage and Packing. THE HOW AND WHY WONDER BOOK OF COMMUNICATIONS

Written by WILLIAM BOWEN-DAVIES Illustrated by EDWARD MORTELMANS

TRANSWORLD PUBLISHERS : LONDON The How and Why Wonder Book of Com- munications is not intended as a technical book explaining how complicated apparatus works. It does show you how, for example, , telegraph systems and work, but it mainly looks at the history of how different forms of communication came about and some of the men responsible for them. Communication here is used in the sense of man speaking to man, and not in the wider interpretation including such subjects as transport and language, and the expression of man's thoughts.

Acknowledgements—Mullard Ltd; The Marconi Company Ltd; Hughes Aircraft; The Post Office.

Originally published in Great Britain by Transworld Publishers Ltd. PRINTING HISTORY Transworld edition published 1973 Transworld edition reprinted 1977 Copyright © 1973 Transworld Publishers Ltd. All rights reserved. The How and Why Wonder Book Series is originated and published in the U.S.A. by Grosset and Dunlap Inc., a National General Company. Published by Transworld Publishers Ltd., Century House, 61/63 Uxbridge Road, Ealing, London W.5 5SA. Printed by Purnell & Sons Ltd., Paulton (Bristol) and London. CONTENTS

Page Page WHY COMMUNICATE? 4 Which disaster proved the How did messages evolve? 4 importance of radios and Why do people 'talk' with their operators? 29 hands? 6 Who was the first murderer to be What sound instruments can be caught by ? 30 used for communicating? 6 Why were pigeons used for RADIO TELEPHONY AND communicating? 30 Who invented the ? 30 What was the 'Edison Effect'? 31 9 COMMUNICATION BY WRITTEN WORD How were signals amplified? 32 9 How did the written word come about? What important discovery led to 10 Who was William Caxton? the wireless? 33 How was the written word sent in How did change? 34 1784? 11 How is letter sorting and delivery TRANSISTORS 35 speeded up? 12 THE TELEPHONE AND 38 VISUAL 14 Who was ? 38 What does 'Telegraphy' mean? 14 How did Bell accidentally prove How were windmills used to send his experiment? 38 secret messages? 14 What is S.T.D.? 39 Who invented a mechanical How have developed? 39 telegraph during the French Revolution? 15 How do work? 16 Why was selenium used in television? What is a Cathode Ray Tube? COMMUNICATION BY ELECTRICAL How was the C.R.T. improved? TELEGRAPHY 18 Who first broadcast the Derby What is the Leyden Jar? 19 by television? What Russian proved Ampere's How is the picture formed? theory? 20 Why was Marconi's system superior How were the telegraph and the to Baird's? railway connected? 21 22 Who invented the ? COMMUNICATION BY SATELLITE Who thought of a communications SUBMARINE CABLES 23 satellite? When were the first cables laid? 23 Why use an artificial satellite? What is the difference between RADIO 24 active and passive satellites? Who were the inventors of the How do satellites orbit the radio? 24 earth? How was Maxwell's theory proved? 25 Which important satellites have What did a do? 26 been launched? What did Marconi achieve? 27 When were the Intelsat satellites How did Marconi's equipment launched? save life at sea? 28 Why was circuit tuning important? 28 GLOSSARY Communication has always been essential in times of war. A runner brought the of the Marathon victory; Persian soldiers sent messages by shouting to one another; and Alexander used a horn to communicate with his army.

Why Communicate?

Communication through the ages has From early times man has striven been the transmission of information to increase his How, di,d messagey s range ofr com- between individuals by sound, touch evolve 7 or sight. A man communicates with munication by his fellows for a number of reasons. different methods, with and without He communicates to express his needs, various mechanical aids. In this way, his opinions, his feelings about him- communication gradually became more self, his surroundings and other people rapid, travelling over greater distances, around him. He feels not only for and the use of the written word for himself but for his fellows. messages and history (the passing on 4 of information from one century to battle we get the word marathon another) finally evolved. In time of describing a long race which is used peace, communication has advanced in the Olympics and other races through the necessities of commerce, today. dealing with disasters, and seeking The Persians are reputed to have urgent medical help. All through used a vocal method of signalling by history messages have also played a choosing men with powerful voices and vital role during times of war. Battles stationing them on high platforms have been won or lost through the about a mile apart. Messages could success or failure of urgent information thus be sent over a specified area by being given at the right quarter at the being shouted from one man to an- correct time. In 490 B.C. Pheidippides other, using their cupped hands as an ran 150 miles to get help from the aid to their vocal chords. Alexander the Spartans for the Athenians who were Great used a large horn in his army for fighting the Persians. Another runner, communicating messages over a dis- with news of the victory at Marathon, tance, perhaps the forerunner of the died on the steps of the Acropolis, megaphone perfected electronically after delivering the message. From this many years later. 5 Red Indians used arm and hand movements to "talk" when they wanted to remain silent. For sending messages over long distances they used smoke signals.

Some people communicate with their As man found he wanted to communi- hands as well as cate at greater Why do people with their voice What sound distances . so he "talk" with their , . . instruments can be , , , hands? by emphasizing used for turned t0 more their speech by communicating? mechanical gestures.. Some Red Indian tribes are means to help known to have been able to "talk" him do so. The Red Indians, for with their arm and hand movements. example, used smoke signals, and a This method would be used when drum or tom-tom. The tom-tom was stalking an enemy or game, when the also used in central Africa and was braves could communicate with one made from animal skin which was another without disturbing their stretched over an empty container. quarry. Hand sign language is in daily The beating of this drum by the use as a means of communication with, natives could be repeated from one and between, those who are deaf and village to another to relay messages dumb, over a considerable distance. The 6 whistle has been used by many different centuries. Speaking tubes have been types of people, including policemen used in offices and aboard ships. The calling for assistance or as a warning; end of each tube, usually held in a wall- and referees to govern the start and bracket, contained a whistle, which the halt of play in football. Another sound caller would remove to blow down the instrument is the horn which is well tube and operate the whistle at the other known as an early form of communi- end and attract the attention of the cating out in the open. Still used for person he wished to converse with. hunting in England when the fox is The telephone has of course largely sighted, it had many other uses in the replaced the speaking tube, though past including that for alarm at the it is still used at sea in an emergency, approach of a foe. This led to the when the power supply has failed and trumpet and bugle calls which con- communication is vital between the trolled armies in battle over many bridge, wireless-room and engine-room.

Africans in the jungle make tom-toms with stretched skins, and beat on them to send messages. 7 Carrier pigeons have been used from very early times, and they were particularly valuable in the two World Wars when bombard- ments prevented any other method of sending information.

To help him in his quest for quicker pigeons as messenger carriers until communication, towards the end of the war there were Why were pigeons m£m has SQme. over 20,000 birds for operational ser- used for , communicating? times turned to vice, in the forward lines and else- animals to aid where. They were exceptionally useful him. In early times the Persians used in action, especially during advances relays of messengers on horseback. when other forms of communication Pigeons have a wonderful sense of proved unsure. When even under- direction and by training and attaching ground telegraph cables were shattered messages to them (usually to their legs), by heavy gunfire, wireless signals could great use was made of their ability to be intercepted, and the ground was too fly to a given point. The garrison rough going for a dispatch , of Modena used them to call assist- what other form of communication ance when they were besieged by Mark bettered the safe flight of a pigeon? Antony in 43 B.C. They were used in Dispatch riders, used in both world Syria and Mesopotamia during the wars, and still much in evidence today, Middle Ages and finally their use ex- were equipped with powerful motor- tended to Western Europe. In 1840 cycles : swift and reliable, they formed Hawes News Agency were operating a vital link carrying dispatches from a pigeon service between London and one area of operation to another. They Paris. At the beginning of the First could carry such things as maps and World War the French handed over other bulky papers, which pigeons 15 pigeons to the British Expeditionary could not carry. Their smartness and Force who eventually, through the reliability earned them their good Signal Service, expanded the use of reputation in both world wars. 8 Communication by Written Word

Through history and records man has Age in Crete, pictorial writing in learnt about the copper, silver and gold was used. In How did the written , Yir.t. * 781 B.C. the Chinese recorded an word come about? Past" Without the early writings eclipse and the art of writing was of clever men like Aristotle, and other introduced in India in 600 B.C. His- great philosophers, education would torical records, such as the cave draw- possibly not be what it is today. ings by Stone Age Man at Altamira in Man's thirst for knowledge increased , were a form of communica- as more was made available for him to tion down through the ages telling us learn. As early as 3500 B.C. the Sume- something of the thoughts of primeval rians produced writings on baked clay. man. Papyrus was used by the early Five hundred years later the Egyptians Egyptians for writing on and was ob- had perfected hieratic writing. At the tained by criss-crossing and beating out the stems of the papyrus plant. same time, during the early Minoan

SUMERIAN BAKING CLAY

Communication by writing and drawing evolved over the ages in different places Quills were sharpened by knives to make pens—hence the Monks produced beautifully decorated manuscripts by hand word "penknife". before printing came into use.

T'sai Lun, a Chinese, invented paper lettering book jackets and advertise- just prior to the Chinese Era, and the ments. Lead pencils date back as far as Moors brought it to Europe around the 16th century, but reliable ones 800 a.d. Ink used by Greeks and were produced in France in 1795 by Romans was from cuttlefish and their M. Conte. The Conte pencil is well pens were usually from hollow reeds known to artists to this day. and bamboos. Quill pens date back as far as the 7th century. The end of the Eventually people got tired of writing quill was sharpened with a knife which by hand and Who was gave us the name "penknife". William Caxton ? looked for an The quills were taken from geese wings. easier and In 1780 steel pens made their appear- quicker method. Writing a letter was ance. At first they were too expensive one thing but what of producing a book to be popular until machines turned or pamphlets? The monks no doubt them out forty years later. In 1884 enjoyed their laboured task of illumi- L. E. Waterman patented the first nating those magnificent bibles in their fountain pen. Fountain pens were of monasteries, but in the outside world course ultimately followed by the ball men were impatient for progress and point pen which is now mass produced turned to a machine of some sort at a very economical price. The Chinese that would simplify and hasten their calligraphers still use a brush for let- task. Printing is thought to have tering as do most commercial artists for appeared in Holland about 1445. The 10 Mail was transported by post boys who blew a horn to herald An early printing press at work. their approach. first British printer William Caxton set Having written correspondence, how up a printing press in Westminster was it to be in 1477. Power presses were in- vented in James Watt's time and in first mail coach 1814 two were made for The Times appeared on 2 August 1784, run- newspaper by the German Friedrich ning from Bristol to London, the 116 Konig. Rotary presses, where the mile journey taking 17 hours. This time printing matter rotated on a cylinder as was later to be speeded up to over 10 compared to being on a flat surface as miles per hour when improvements in the earlier type-setting, came into were made to the roads. The advent being during the middle of the 19th of the mail coach is said to have century. The type, however, was still been the idea of John Palmer. Before set by hand. Machines to set the type this time mail was entrusted to post did not appear until Ottmar Mergen- boys mounted on horse-back. The mail thaler produced them during the 19th bag was strapped to their backs and century. Printing produced books, they heralded their approach by handbills, pamphlets, almanacs and means of blowing a horn. John newspapers. A more personal machine, Palmer felt that the mail would be the typewriter, was invented by safer in the hands of armed guards in a Christopher Shales around 1868, which stage coach, and he made the sug- became the Remington typewriter in gestion to William Pitt, then Chancellor 1878. of the Exchequer. 11 Mail being sorted en route by rail.

In Great Britain today, about 28 equipped as moving post offices where million of the further sorting is carried out while the How is letter letters collected train speeds on its way. In London, the sorting and delivery speeded up ? from post boxes post offices have their own under- all over the ground rail system where mail can be country have to be taken to a centre quickly transported between sorting where they are sorted to the different offices and the main line stations. areas where they are to be dispatched. With the advent of micro-photo- We have all seen, at some time or graphy, the written word could be other, the mail bags in which letters photographed and reduced in size to be are placed and transported from sorting stored away for record purposes, saving offices and dispatched to the railway a good deal of space. This principle stations for transport to other main was used to great advantage during the offices. What we most likely have not Second World War, when it was seen is the British Rail trains which are important to keep up the morale of 12 fighting men abroad by ensuring that The Air Mail system has greatly they had written contact with their speeded up the dispatch of letters friends and families at home. The overseas. The first air mail in England Airgraph System whereby the service- was flown between Hendon and Wind- man could write his letter on a single sor in September 1911. Even with the sheet of paper, which was photo- speed of air mail it still takes time to graphed, reduced in size, and flown get a message across any distance. home by air mail to the relatives, was a Any urgency calls for speed. The ideal great boon to him as to his family. It situation is the instant reception of a might be a matter of years before he message urgently transmitted. In order saw them again, but at least they knew to achieve this man invented telegraphy he was well at the time of writing. in many forms.

The first air mail in England was flown in 1911 between Hendon and Windsor. 13 Visual Telegraphy

The word telegraphy or telegraph is In 1575 British ships set their sails to derived from two give specific What does Greek words How were windmills meaning and "Telegraphy" mean? used to send secret fired a cannon to Tele meaning messages ? attract attention. "far" and "Graphos" meaning "writ- Many years later, during the Second ten". Thus telegraphy could be inter- World War, partisans used a different preted as a written message, or signal, type of sail setting for messages, that being sent over a distance. In 150 B.C. of the windmills of Holland. This way the Greeks used a signalling system the underground movement was able where lighted torches were placed be- to carry messages used against the tween the gaps of two walls. The gaps German occupying forces. This was in one wall represented the line of the no new means of signalling for code they were using, and the gaps in the Dutch who have used different the second wall represented the letter positions of windmill sails for indicating in that line. In this way the letters of the events of birth, marriage and death the message were spelt out by torch- for many years. light. Fire was another means of signal- y/r/z rr, ling. At the time of the invasion by the Spanish Armada, were placed around the English coastline to warn inhabitants of the approach of the Spanish ships. This type of telegraphy was known as optical or visual telegraphy. At the battle of Salamis, in 480 B.C., the Greek ships were outnumbered by the Persians and things looked bad for the Greeks. An unexpected signal from their flagship ordering all the ships to turn and face the Persians who were encircling them, surprised the Persians and threw them into confusion. The use of flags later spread to Europe. They were used by the Romans on their military standards, and Brutus in 49 B.C. used flags on his ship which The Greeks turned defeat into victory by following orders could easily be recognized. signalled to them by their flagship. 14 Napoleon's soldiers operating 's signalling machine.

The year 1789 saw the beginning of the one at each end. The pivoted beams French Revolu- were controlled by copper wires and Who invented a tion —and an pulleys operated by handles at the mechanical telegraph , , f base of the machine inside the tower. during the French Ur?ent need for As many as 196 different positions Revolution ? quick communi- could be made with the pivoted arms cation in the giving up to that number of signals. campaign. Claude Chappe, a French- The signal arms were constructed man, saw the need and with the help to minimize wind resistance and of his brother and others, produced a painted black for easy recognition. machine which was accepted by the Legislative Assembly in 1792. Set on a The signals from one tower were read tower, it consisted of a central vertical from another tower by means of a beam, at the top of which was pivoted telescope and a chain of stations a crossbar. At each end of the crossbar radiated from Paris and reached out to two more pivoted arms were attached, other cities in other countries. 15 kM^iitm *

Gamble's six-arm was mounted on carts and used in the field by the army.

The semaphore was introduced in years after his untimely death in 1805. England in 1795 by the Rev. Lord When other scientists and inventors George Murray. It consisted of a screen realized the potential of electricity as a with six shutters which was operated to means of improving telegraphy the give 63 combinations. The boards were days of the manually operated visual pivoted and moved by cords. The telegraph were on their way out. Admiralty used it to operate from London to various relay stations along Before we pass on to electrical the coast. A message could be sent telegraphy let us How do between London and Portsmouth in heliographs work? consider visual a matter of minutes. John Gamble in- telegraphy by vented a six-arm semaphore at about reflected light. We have seen how the the same time as Lord Murray invented Greeks signalled by torches in the dark, his. This machine consisted of a vertical but what of daylight signalling? We all post with three arms either side. It was know that by taking a simple hand tried by the army in 1797 and employed mirror and catching the sun's beams for field use mounted on carts or directly on to it we can direct a very coaches. Used with a telescope it had bright spot of light on the walls or a range of five miles. Chappe's aerial ceiling of a room from sun shining telegraph system survived for forty through the window. 16

-COM-B In 1821, a prototype was admit or obstruct reflected light invented by Gauss. It consisted of two through the screen. All mirrors used mirrors which were placed at right in the apparatus, as in the case of the angles to each other. One mirror was Mance heliograph, had a hole or circle used for focusing, the other for signal- in the centre, so the operator could ling. Several different types of helio- focus the mirror on to the station to be graph were used for signalling in signalled to. The pencil of light pro- different theatres of operation. Mance's duced by these methods had the Field Telegraph employed a sighting advantage of directing the beam where rod in addition to the signalling intended and so providing security mirror. Begbie's Field Telegraph used against the interception of the mes- two mirrors, one as a "sun mirror" sages by the enemy. to reflect the sun on the signalling Visual signalling played an important mirror, should the sun be behind the part in the South African Wars. The signaller. In addition the signalling degree of sunshine and clear atmos- mirror was kept static, so that it was phere was ideally suitable in that not out of alignment with the reflected country for visual signalling of sun's rays, keying being carried out all kinds. In clear weather, using on a screen placed a few feet in front heliographs, distances of 50 miles of the signalling mirror. Attached to the could be obtained without the use of signalling mirror was a sighting arm binoculars. Over hilly country, dis- with a sight to keep the reflected sun's tances of 100 miles were reported. rays in line with a hole in the screen. Transportable semaphore was used The reflected light could then be broken extensively in South Africa to- up into dots and dashes by means of gether with flags of different a key which could be operated to size.

During the South African Wars British soldiers used heliographs to signal to each other. 17

COM-B Towards the end of the 19th century on sea patrol and on merchant ships in limelight lamps were used for signalling convoy. Ships could communicate with by day as well as by night, using the aircraft as well as with other ships. Morse Code. Signal lamps using The Aldis lamp was held up to the shutters were employed by warships in eye, focused on the object to be both world wars and, during the Second signalled to, and was operated by World War, the Aldis lamp, with tele- a finger trigger which deflected scopic sights, was used to great the light by means of a movable advantage by signallers aboard aircraft reflector.

Communication by Electrical Telegraphy

Those enterprising men, the Greeks, poles repel, whereas different poles will not only discovered that when pieces attract. It was through simple experi- of amber were rubbed with material ments such as these that our forefathers they picked up small particles, such as gradually built up discoveries which fibres, but also in the area of Magnesia led to the use of electricity in com- were stones which, when placed near munication and other services. pieces of iron, attracted them. So it is from the Greeks that we get the name "electricity" and electron. They called amber "electron". We call the electron a unit of negative electricity. Matter we find is built up out of a number of electrons circulating about the positive nucleus, which comprises the atom. N From Magnesia, we get the term magnetism, which is caused by magnets which attract metals to them. If you take a comb and pass it several times through your hair, and then immediately put it on a small piece of paper, one end of the comb will attract the paper. You have charged the comb with positive electricity. If you take two identical magnets, each with a north and south pole, and place them Above—the composition of an atom. Below—attraction by two dissimilar magnetic poles; repulsion by two similar near together, you will find that like magnetic poles. 18 At Leyden University in 1746 Pieter effect the first electric battery, and was Van Musschen- constructed of zinc and silver discs set What is the i , c , ,, alternately, and separated by pieces Leyden Jar? broek found that by charging a of moistened cardboard. His theory glass jar partially filled with water, he was that when you placed two dis- was able to store electricity. Forerunner similar metals in contact with one of the condenser storing electricity, the another you caused an electric current apparatus became known as the Leyden to flow. To Volta went the honour of Jar. In England Henry Cavendish set having the unit of electricity, the Volt, about improving the Leyden Jar by the named after him. use of tinfoil on its inner and outer In 1820, a Danish physicist by the surfaces. name of Oersted proved that a mag- This system had two main problems. netic needle of a compass was affected Firstly, the electrifying machines for by the current passing through metal charging the Leyden Jar were rather placed near it. Later this led to the cumbersome pieces of apparatus, and invention of electro-magnets which secondly, the jar itself would only were to prove invaluable for operating supply electricity for a very short time. the telegraphic circuits. An electro- Alessandro Volta, an Italian professor, magnet can be produced by wrapping found an answer to this by his inven- a coil of wire around a piece of soft tion of the Voltaic Pile. This was in iron and passing a current through that 19 NEEDLE

The Cooke and Wheatstone five needle telegraph. wire. Whether the piece of metal is in could be obtained by making the wire the shape of a bar magnet or a horse- carrying the current in the form of a shoe magnet, a north and a south pole coil. His took the form of will exist at either end of the magnet. ten keys, like a piano, which could Ampere, a French physicist, with transmit ten different signals along advice from Pierre Simon Laplace put wires to five different coils at the forward the idea of passing a current receiving end of his apparatus. Inside through a number of wires, one for each coil was a. magnetic needle which each letter of the alphabet, and termi- could be deflected two ways from the nating them at the receiving end with north-south position, depending on the a compass needle to each wire. In this direction of the current sent through it. way a message could be sent. Ampere's The direction of the current was deter- name gave us the unit of current, the mined by which key was pressed at the ampere (shortened to amp.). transmitting end. Thus it was possible to send ten different signals. He first Paul von Schilling-Cannstadt, a demonstrated his apparatus at Bonn Russian, put in September 1835. A year later William What Russian Ampere's idea Cooke, the son of an English doctor, proved Ampere's . saw some experiments by Professor theory7 into practice. He also took note of Munke at Heidelberg with Von Schil- ling's telegraph. At Heidelberg he the discovery that a stronger current 20 _

experimented on the idea himself and project was that they were now using a on his return to London he spent the two needle telegraph which indicated rest of the year working on the inven- each letter by a pre-arranged code tion of a new telegraph, encouraged by determined by the momentary deflec- Michael Faraday, the famous Professor tion of the needles. The previous five of Chemistry. needle telegraph was so constructed that the required letters were indi- In 1837 Cooke formed a partnership vidually indicated by two of the with Professor five needles pointing in opposite How were the Charles Wheat- directions towards the required letters. telegraph ahd the , stone railway connected? > who was Requiring five lines instead of also experiment- two, these earlier models were too ing with telegraphic apparatus, and expensive to operate over long dis- between them they applied for a patent. tances. It is interesting to note that in Robert Stephenson, Chief Engineer to 1845 the two needle instrument at the Railways, was approached and in Paddington was responsible for the autumn of the same year an receiving a message concerning the experimental telegraph line was laid murder of Sarah Hart at Slough. down by Cooke between Euston and Her murderer, John Tawell, was Camden Town. The following year he arrested in Cannon Street, and later laid another telegraphic line between was convicted and hanged. The Paddington and West Drayton which instrument used for the reception of was later carried on to Slough. The the message can be seen at the Science Museum today. interesting point of this particular What is it? How did it originate? For The original CQD, this refer to an which was followed later by the three Who invented the American artist dots and three dashes followed by Morse Code? who displayed an three more dots, standing for the mari- interest in telegraphy. He used his own time S.O.S., must have saved countless easel to make the frame of an apparatus lives after Marconi had made wireless which could record signals on paper telegraphy possible many years later. every time his morse key was pressed, Morse received great help from Joseph sending a current through his appara- Henry, another American, who showed tus to actuate an electro-magnet which him how to increase the range of his guided a pencil onto a strip of paper, telegraphy by means of relay-electro- which passed over a revolving drum. magnets inserted in the telegraphic Zig-zag lines were formed which line. suffered hard- could be read as a coded message. ships and disappointments in much The name of this man was Samuel the same way as his predecessors Morse, and his famous Morse Code in the field of invention, but finally was to be used on his own apparatus he triumphed, and before he died as well as on other telegraphy machines in 1871, a network of telegraph before being used in wires spread across America carrying itself. messages.

A • - !_• — •• B M - - V C N - • W D 0 X E • p Y F Q z G R H S • • • 1 • • T - J U K

Samuel Morse ingeniously invented an apparatus that could record signals on paper. His famous Morse Code is still widely used. 22 The steam tug Goliah had great difficulties in laying the cable across the English Channel.

Submarine Cables

The first men to lay a cable under the 1851 which was still in good working sea from one order 10 years later. When were the , . ,1 first cables laid? COuntry to the The first cable across the Atlantic other were the from Valentia Island to Newfoundland Brett brothers, John and Jacob, be- was laid by H.M.S. Agamemnon tween Dover in England and Cap Gris- (British) and the Niagara (U.S. frigate) Nez in France, in August 1850. The in August 1888. The line went dead in cable was covered with gutta-percha, a October that year. Another cable, substance from certain trees in Malaya thicker and stronger than the previous which insulated the cable. The action one, was made and was finally success- of water actually hardened the surface fully laid by Brunei's famous steam of the material, and gutta-percha was ship the Great Eastern in July 1866. used for many years until polythene The Post Office have three cable- sheath took its place. laying ships, one of which is the A steam tug called the Goliah was Alert. She is painted a reddish-orange used for carrying the cable, and paying to warn shipping in the vicinity to keep it out across the English Channel, and clear of fouling the cable being laid. it was escorted by the survey vessel The modern transoceanic telephone H.M.S. Widgeon. Unfortunately a cable is covered in polythene in place French fisherman fouled the first cable, of gutta-percha and is of coaxial but another one was laid in November construction. 23 Hertz's apparatus used a Ruhmkorff coil and a secondary circuit to transmit high-frequency oscillations which were detected by sparks on a broken loop of wire.

Radio

Radio has been about the most im- great foresight to put many experiments portant discovery in the story of Man and instruments together to finally and Communication. Because of it man produce a commercial proposition over has been able to communicate more land and sea. We must not forget the speedily over much greater distances many other men who by their experi- than ever before and has been able to ments and inventions made this pos- do so without the aid of telegraph wires sible. As far back as the 17th century or undersea cables. The discovery of Huygens, a Dutch scientist, put for- radio was also necessary for your ward theories that light was a form of television programmes of today, which waves in the ether. Later Michael require the transference of sound as Faraday, Fellow of the Royal Society, well as vision from the transmitter to endeavoured to prove that lines of your receiver. Without radio it would magnetic force existed in the ether have been impossible to keep contact when an electrical force was applied with the astronauts on their journey to between two objects. Faraday's pupil, and from the moon. James Clerk Maxwell, proved this mathematically and in 1873 produced a People equate the name Marconi with treatise on light and electromagnetic the wireless, later waves. He maintained that it should be Who were the called the radio. possible to produce invisible electro- inventors of the magnetic waves which differed only in radio? Marconi was the man who had the frequency from light waves, and which 24

25 Early radio sets, such as crystals, were equipped with earphones for listening.

travelled at the speed of light, actually being transmitted he made a approximately 186,000 miles per circle of wire which he broke at one second. point to insert a metal ball at each end of the loop. This was his receiver In 1888, a German professor named which he held a few feet away from his Heinrich Hertz transmitter. On closing the primary How was Maxwell's i circuit of the Ruhmkorff coil, that is theory proved? proved Maxwell s theory in practice applying power from the battery, by producing these electromagnetic sparks flew across the secondary circuit waves. By using a battery combined to be picked up by the simple receiver with a Ruhmkorff coil he was able to which discharged across the spark gap produce a high voltage across the in its broken circle of wire. secondary coil sufficient to cause sparks Before Marconi appeared On the to fly across a gap in the secondary scene, William Crookes, knighted in circuit. In order to detect that the 1897, suggested using electromagnetic electromagnetic lines of force were waves for signalling. 25 WIRE IS ATTACHED TO BOTH THE TERMINALS. THE OTHER ENDS OF THE WIRES ARE ATTACHED TO A RECEIVER CIRCUIT.

Oliver Lodge was the first man to receive signals through his 'coherer' apparatus.

A French professor of physics named A signal received at the aerial would Edouard Branly cause the filings to cohere, thereby What did a coherer do ? experimented allowing the circuit to be closed with a glass tube between battery and bell. filled with metal filings and found that Observe how internationally this when a spark was discharged near great event is building up: Huygens, them, the filings cohered (stuck to- a Dutchman; Faraday, Maxwell, Oliver gether), and allowed a current to pass Lodge, Englishmen; Hertz, a German; through them. Branly, a Frenchman. Now a Russian In 1894, Oliver Lodge, a British appears on the scene, a scientist named scientist, realized that it was possible Popov. Popov was studying natural to use the coherer as a Hertzian wave electrical discharges in the air, and for detector. He named Branly's apparatus this he used an elevated wire. Later a "coherer" and using this and im- Marconi used the same idea for use as proved of his own, became the an aerial for his receiver and trans- first man to receive signals through this mitter, to give him much greater range. type of apparatus. His improved co- Marconi also used the American's herer automatically dislodged the filings Morse Code for signalling, with great after a signal had been received, so that success. Each man, and many others, the coherer could receive the next contributed something to this gigantic signal. By putting the coherer in series jig-saw, the answers to which were with a battery and electric bell it was going to spread eventually all over the possible to recognize the presence of world and later to the moon and the signal by the sounding of the bell. beyond.

26 I Experimenting and improving on all lines. Later Marconi's apparatus was the apparatus he tried out on Salisbury Plain before What did important officials from the Post Office, Marconi achieve ? could produce and receiving army, navy and government. Amongst encouragement from another Italian, the officials was a naval officer named Professor Righi, who had also worked Captain H. B. Jackson, who had also on the reproduction of electromagnetic been experimenting with radio. Mar- waves, Marconi worked at his parents' coni's experiments were a success and home in Northern Italy. Using an later, on 20 July 1897, he formed his aerial, induction coil and coherer, de- first Wireless Signalling Company. In coherer and spark gap, he managed Italy he managed to make possible to bridge a distance of several miles. radio communication between the land In 1896 he decided to bring his and an Italian warship twelve miles equipment to England. To protect his offshore. Back in England the first two invention he first took out a patent. He permanent shore stations were estab- was introduced to Sir William Preece, lished with his equipment at Alum Bay, Chief Engineer to the G.P.O., who Isle of Wight, and Poole harbour near allowed him to demonstrate his appara- Bournemouth in August 1898. Ships tus, with success, on the roof of the fitted with his equipment were able to G.P.O. Headquarters at St. Martin's-le- communicate with them. Two more Grand in London. Sir William Preece stations, for demonstration purposes, himself had been experimenting for were operated for Lloyds at Ballycastle some time with the induced current and Rathlin Island, Northern Ireland, produced between parallel telegraph in May 1898.

Marconi demonstrated his equipment before Service chiefs on Salisbury Plain. 27 When the sank the wireless operator, Phillips, sent out distress signals to the very end.

One of the first records of life-saving at the sets were not selective enough, too sea by his wire- much interference was caused by the How did Marconi's less equipment broad waveband they used. So Marconi equipment save life at sea ? was when the then bought up the patents relating to East Goodwin circuit tuning which Sir Oliver Lodge lightship was rammed by the freighter had previously been experimenting R. F. Matthews in 1899. Fortunately, with. Adding his own ideas to improve during the previous year both the circuit tuning, Marconi produced, in lightship and South Foreland lighthouse 1900, his famous "four sevens" patent were fitted with Marconi apparatus, (British 7777). He also formed an which enabled help to be sent to the additional company, the Marconi Inter- ship in distress. Range at sea, by radio, national Marine Communications was extended to 74 miles, but Marconi, Company Ltd., with the object of as ambitious as ever, still looked for building shore stations first at home greater achievements. He needed more and then later abroad. Marconi equip- capital and in 1900 he changed the ment was rented to shipping companies name of his company to Marconi's and trained Marconi operators were Wireless Telegraph Co. Ltd. supplied to the ships, an arrangement which works to this day. With the As more and more were success of tuned circuits, which, besides built, both here cutting down interference, also in- Why was circuit creased range, Marconi set about in- tuning important? and abroad, it was found that creasing the distance of transmission 28 Atlantic. It was fortunate for Marconi that he had Ambrose Fleming as his technical adviser, for Fleming was to produce one of the greatest techno- logical discoveries of our age. Up to now transmitters and receivers had been confined to the use of the Morse Code, or other codes, which were either recorded on an ink printer or read by an operator by the use of a sounder or headphones. This was all very well for the sending and receiving of messages but not for general broad- casting to the public. Before passing on to the next great step in radio dis- covery let us pause and look back awhile on the practical effect Mar- coni's radio had on the world and how he and others strove to increase its He achieved a distance of about 200 effectiveness. miles, first of all, between a temporary station at the Lizard, Cornwall, and the The terrible disaster of the great British Isle of Wight station. Encouraged by liner, Titanic, this, and with the aid of Ambrose Which disaster proved the abso- proved the , , c Fleming, he built a powerful trans- lute importance of radios necessity for mitting station at Poldhu, also near and radio operators? Carrying radio the Lizard. In September 1901, the equipment and a masts of the Poldhu station were sufficient number of operators to keep wrecked in a storm, but after being re- watch for distress signals. During that placed with a simpler aerial, Marconi cold night in April 1912, S.S. Titanic and his two assistants, Paget and Kemp, struck an iceberg and 1,503 people took their equipment to Newfoundland were drowned. The wireless operator, and set up a temporary receiving station Phillips, continued to send out distress on Signal Hill, St. John's. For an aerial, signals using both the old code CQD to gain height, they used first a bal- and the new one, S.O.S., with the loon, and then a box kite. On 12 result that 705 out of a total 2,208 December 1901, at 12.30 p.m., Mar- aboard were saved by the ship coni heard through his earphone the Carpathia who answered the call. Many pre-arranged signal of three dots, more lives would have been saved had representing the letter "S" in the Morse the ship Californian, which was nearer Code, coming from the Poldhu trans- at the time, had her operator on watch. mitter over 2,000 miles across the Unfortunately, he had just completed 29 an exceptionally long watch prior to Dr. Crippen who was making his the distress calls being sent out. It getaway aboard the ship Montrose. took time, but in years to come, By means of radio, the ship's captain International Law required constant was warned, preventing the criminal's watch for deep-sea vessels, whether by escape. Dr. Crippen, like John Tawell operators or an automatic alarm before him, who was apprehended system, whereby the transmitted S.O.S. by the use of the electric telegraph, signal would activate the alarm on had also murdered a woman, only ships within wireless range whose this time it was the murderer's own operators were off watch. wife. Once again justice had prevailed by a few taps on a Morse key. Later, Another great proof of Marconi's suc- as we shall see, the police would owe cessful much to the assistance of radio. Who was the first apparatus murderer to be was the capture caught by wireless? of the murderer

Radio Telephony and Broadcasting

We have seen how communication by of superimposing the audio frequency radio telegraphy, (or speaking waves) on to the high Who invented the frequency (or carrier waves) which telephone? the use of appa- ratus capable of would take the audio frequency wave sending and receiving the Morse Code, through the ether to a point where it was gradually spreading further and would be picked up by a suitable further afield. But man had not detector and turned back into audio properly conquered the ether with his frequency waves suitable to be trans- voice. In 1875, a Scot named Alexander mitted to the ear via earphones, Graham Bell, living in America, had similar to the telephone earpiece. The invented a practical telephone, where- waves produced by Marconi with his by man could communicate vocally, spark transmitters were totally unsuit- but over a land line. Another man, able for carrying the audio frequency David Edward Hughes, invented a wave produced by a microphone. What microphone. What was now needed Fessenden wanted was something that was something to connect microphone would produce an undamped or con- and earphone through the ether in the tinuous wave, and he experimented same way that they could be con- with an arc transmitter with this end nected by land lines. in view. He was closely followed by In 1902 Professor Fessenden, the Valdemar Poulsen, a Danish scientist, Canadian, was working on the problem who also experimented with an arc 30 transmitter to produce radio telephony. the carbon filaments used in the bulbs Fessenden found that the oscillations caused a blackening of the glass sur- (the swing between two points) from face. To try to prevent this he lined his arc were too weak, but still working the inside of the glass with tinfoil only on the problem, he designed, and to find that if he connected this tinfoil Alexanderson, an engineer, built a high to the positive terminal a current frequency alternator of sufficient power flowed between the two, tinfoil and to produce a carrier wave. On Christ- filament. However, on reversing the mas Eve 1906 wireless operators were connections he found that no current greatly surprised to hear speech and flowed. This happened in 1883. In music breaking through their watch for 1904 Ambrose Fleming considered Morse Code signals. putting this flow of current in one direction to a practical use, and Two years prior to this Ambrose through it he produced the first valve Fleming was for radio, called the diode—because it What was the • j • ^ consisted of two elements, the filament "Edison Effect"? considering the and the plate (or anode as it is termed curious "Edison today). If current through it travelled Effect". Both he and Edison had pre- in one direction only then here was an viously been concerned with the peculi- opportunity for "rectifying" the high arities of the electric light bulb. frequency alternating wave into current Edison, in America, had found that

Fleming's diode valve and Edison's electric light bulb. 31 FILAMENT

ANODE

GRID 's audion or triode valve.

pulsating in one direction only. Any other detectors all failed to do. To variation in the strength of these achieve this he experimented and found pulses, if low enough in frequency that by inserting a "grid" between the (such as Morse Code signals or speech cathode, the negative pole of current, and music frequencies), could be used and anode, the positive pole, and by to activate the earpieces of a pair of applying a weak signal to this he was headphones. Of course the signals able to amplify it. The charge on the would be weak, and a great deal would anode was positive. By making the grid have to be done to amplify them, both positive he found that it helped the in the construction of the valve and im- flow of electrons from cathode to provement to the circuit. Yet another anode. By giving the grid a negative detector was discovered, this time by charge it reduced the anode potential, H. C. Dunwoody and G. W. Pickard, as it acted as a barrier to the flow who found that by touching certain of electrons from the cathode. The crystals lightly with a wire they would grid then formed a control of the rectify radio signals, that is turn flow of electrons from cathode to alternating high frequency currents into anode. This method enabled him unidirectional currents. to decrease or increase (amplify) the incoming signals. Lee patented It was left to an American, Lee his "audion" valve, as he called it, De Forest, to in January 1907. Today we call a How were signals three electrode valve a triode, but it amplified? find a way of amplifying is a much more sophisticated valve than the one Lee Forest made. (strengthening) the signals, which the 32 In 1913 another brilliant discovery was neither is an amateur, or "ham", as made, that this he is known, allowed to operate his What important triode CQuld be transmitter without a licence. discovery led to , ... made to the wireless ? oscillate, In America, Dr. Frank Conrad was that is to produce using gramophone records over his undamped waves which could be used experimental radio-telephony station, for transmission. This meant that later which was listened to by people with the large arc and other high frequency crystal sets. In England, Captain transmitters could be replaced by much Round of Marconi's was also engaged smaller valve transmitters, having the in radio-telephony, and in 1920 test same, if not greater range than their transmissions from Chelmsford were predecessors. After the First World received across the Atlantic. In Eng- War, broadcasting to the public was land, the 15 kilowatt station at Chelms- being seriously considered both in ford broadcasted mainly news items Great Britain and in the U.S.A. Both and music. Dame Melba, the singer, countries forged ahead, with the differ- on one occasion broadcasted "live" on ence that whereas in America there was this early system, with a microphone little or no control, in Britain broad- consisting of a carbon earpiece and a casting was subject to strict licensing trumpet fashioned from a cigar box. by the G.P.O. Even to this day a The result was so encouraging that wireless operator is not allowed to another station, 2MT, was installed at operate aboard ship without a licence Writtle, just outside Chelmsford. The issued by the Postmaster General, and east coast area, being flat, was found

Dame Melba singing into an improvised microphone which was partly made from the wood of a cigar box.

1H.4W.-C0M-C most suitable for broadcasting. In long-wave high-power station at Chelmsford itself is the original build- Chelmsford ing, the first of its sort for manufactur- ing wireless sets in the world, and Receivers at first consisted of crystal a commemorative plaque is on its sets with head- w r0lesses outside wall. Times change, modern change? ' phones, then buildings are now used for the gradually valve manufacture of wireless components sets powered by batteries and fitted and the old building is now a furniture with loudspeakers appeared on the store for a well known removal market. The early speakers were like firm. enormous horns or ear-trumpets placed Captain P. P. Eckersley played an on top of the sets. The early sets pre- important part in the operation of ceded the more sophisticated models of 2MT and later became Chief Engineer today, mains sets, where one only has to the B.B.C. which was formed in 1922 to connect the set to the mains and push from the many firms that started manu- a button to turn the set on. The old facturing wireless sets. To serve a wider battery sets required three sets of bat- area, another station, 2LO, was erected teries : a high tension of 120 volts con- at Marconi House in the Strand, Lon- nected to the anodes of the valves; a don. Afterwards, the B.B.C. erected wet accumulator, low tension, of 4-6 eight medium wave stations at different volts, to heat the filament; and a dry points in the country, retaining the battery of 9 volts, for the grid bias.

Three wireless receivers—from the earliest to the present day. 34 Transistors

To deal effectively with the subject of a material, usually germanium (taken transistors would require a book of its from coal) or silica (taken from sand), own. They were invented by three which has a resistance between that of Americans, Bardeen, Brattain and an insulator and that of a conductor. Shockley, while working for the Bell In other words, it will not pass Telephone Company, in 1948. current easily. However, by adding Transistors are very small and have certain impurities to it, in a particular the advantage over thermionic valves way, the number of free electrons that, having no filament to heat, in the semi-conductor either becomes they operate instantaneously. They less (making it P-type material) or is function with a battery of considerably increased (making it N-type material) less voltage than a high tension battery according to the substance added to it. required for thermionic valves, and By fusing together, in a special manner, these batteries are also longer lasting. a piece of N-type and a piece of P-type Like the portable transistor radios of material, a flow of current will occur, today, the batteries in the early models basically in one direction through them. had to be replaced when worn out. We have here the equivalent of the What was more, in these early models diode valve. the accumulator had to be re-charged, Like valves, the conventional tran- which was a messy business as it con- sistor has three electrodes, an Emitter, tained dilute sulphuric acid which a Base, and a Collector. Although these would burn material if it was exposed three electrodes do not operate in the to it. Transistors are now used in both same way as the Cathode, Grid and radio and television and many other Anode of the triode valve, they electronic devices, such as record resemble their function, namely the players and computers. control of electrons to detect and Early transistors worked on the amplify signals. The transistor using principle of two wires pressing on a three electrodes (a triple sandwich— flat piece of germanium. Although P-N-P type or N-P-N type) as com- perhaps an improvement on the old pared with the diode's two pieces of "cat's whisker" galena crystals, this material (P-type and N-type) was made point of contact method was not and produced in different ways. efficient and was subject to noise effects. One complex method is the Silicon To begin to understand the working Planar transistor. Here the collector, of a transistor one must know the base and emitter are manufactured in meaning of a semi-conductor, which is layers. The process calls for very 35 Transistors can be made so small that they can pass through the eye of a needle.

detailed work, starting with a thin slice nected to a metal surface deposited of silicon, about 5 cm. in diameter. through more windows made in the The surface of this piece of silicon is oxidized surface. The piece of silica is oxidized, windows are cut into the now cut up into anything up to 6,000 oxidized silicon, the surface cleaned transistors, each one being tested before and an impurity is fused into the being cut by a diamond cutter. We have silicon to form the base. The surface is in effect a means of mass production of then oxidized again, more windows transistors of the smallest size imag- are etched again in the oxidized surface inable which are then bonded, collector and the emitter plane is diffused into side down, on to a stem or header, the base. We now have our three which is gold-plated. Gold or alumin- electrodes, forming the N-P-N or ium wires are used to connect the P-N-P sandwich. Final processing in- base and emitter to the lead-out cludes the making of electrodes con- wires, they are examined, washed 36 Telstar being launched by a three-stage rocket from Cape Kennedy.

and dried and finally encapsulated. Today modern wireless transmission Planar techniques led to the creation plays a great part in our lives, and not of the integrated circuit in which tran- only for entertainment. With the use of sistors and components could all be short waves important messages can be diffused into a piece of silicon small flashed around in seconds, not only to enough to pass through the eye of a other lands at the far corners of the needle. This chip, as it is called, earth but to ships at sea sailing to can contain as many as hundreds those lands all over the world. More of components, and as an integrated recently we have seen the advantage of circuit can be used to good effect artificial satellites such as Telstar, in radio receivers, amplifying circuits which give us improved reception not and computers. The integrated circuit only on this earth but from space shown in the illustration is before craft circulating and landing on the encapsulation. moon as well. 37 Alexander Graham Bell 'accidentally' calls his assistant by telephone for the first time.

The Telephone and Teleprinter

Alexander Graham Bell, born in were impinged upon it. This led eventu- Edinburgh in ally to the original telephone earpiece Who was Alexander Graham Bell? 1847, invented which he and his assistant Watson the telephone later perfected enough to make the while in the United States of America human voice audible over a land line. in 1875. Interested in music and the human voice, he taught elocution and The tale goes that while working on tried to make a musical telegraph, for his apparatus which he received financial backing How did Bell Bell, thinking accidentally prove from various Americans. In the course his experiment 7 Watson was in of his experiments he made a mechani- the room, said cal ear, which contained a diaphragm "Come here, I want you". Watson which vibrated when sound waves came, but only because he was listening 38 on a vibrating diaphragm in a different miles of wire for telephonic use. In this room downstairs. Like all inventions way not only are thousands of tele- the apparatus had to be perfected and phone circuits provided, but many then sold to the public. Difficulties, television channels as well. financial and otherwise, had to be over- The original telephones required two come. The first telephone company was wires for conversations between two registered in Britain in 1878, and it subscribers. Now, due to such innova- opened its London exchange in August tions as Carrier Working with coaxial the following year, with a handful of cables and Pulse Code , it subscribers. Fearful of the fate of is possible to have a number of tele- its telegraph service, the Post Office phone conversations carried on simul- managed to get a High Court ruling taneously, using the same conductor. that, for the purpose of the Telegraph By the use of cable and wireless, Act, telephone and telegraph were the telephone conversations can be carried same, and in this way all telephone on over great distances and radio companies had to operate by licence telephony can be used aboard ship and, from the Postmaster General. On 1 more recently, in private cars. Taxi January 1912 the G.P.O. took over the cabs, police cars and private aircraft telephone systems with the exception have their own systems contacting them of two, owned by the corporations of to their respective bases. Radio-trans- Portsmouth and Hull. Today Hull and ceivers are used in outposts in the out- the Channel Islands still run their own back of and we are all services. familiar with the famous Radio Doctor who flies from one farm to another With continual research the Post Office because distances between farmsteads vastly improved are often as much as 100 miles, making What is S.T.D.? telephone com- communication otherwise impossible. munication, both in this country and The army and police force find walkie- abroad. Today we have over 6,000 talkie short wave sets indispensable for automatic exchanges and around 15| their work. Another useful piece of million telephones operating in Britain. apparatus used by the Post Office is the Subscriber Trunk Dialling (S.T.D.), teleprinter, used for telegrams and now first used in Bristol in 1958, now known as the System. Used both operates over much of the country and at home and abroad each Telex sub- it is now possible to dial direct to scriber has his own machine which Europe and even to North America. looks partially like a large typewriter. The message is typed out, after dialling The 620 ft. Post Office Tower built in the number of the telex system you are central London communicating with, and providing How have telephones ide§ inter_ the other machine is switched on, the developed 7 message is received on it whether any- city one is present at that end or not. links, saving considerably on many 39 SCANNERS MICA SCREE ITHZINC SIL WEABRIGK .UORESCEN .ECTRONIMI

IE SCREEN F ECTRONSTi VRROW BEAI

Left—Baird's original scanning machine. Right—Braun's television tube.

Television

The word television came into being and at the receiver, the one at the re- when used by the Frenchman Perskyi. ceiver being synchronized to follow that He combined the Greek word "tele" of the transmitter to produce the same (at a distance) with the Latin "video" picture. Into the disc he cut a spiral of (I see). holes so that as the disc turned before the object or scene to be transmitted In 1884 Paul Nipkow, a German each hole traced another line of the engineer, scene. In one complete revolution the Why was selenium used in television ? patented his scanning was completed. Nipkow's scanning disc in scanning was exposed to a selenium Berlin, which was later to be used in screen. Selenium, it was found, had the television to good effect by John Logie property of varying its resistance to the Baird, a Scottish inventor whom we flow of current according to the amount shall discuss later. Very briefly, Nip- of light shining upon it. In this way, kow's system was an apparatus using a degrees of light and shade of the revolving disc both at the transmitter scene to be televised could, by reason 40 positively charged. The glow produced on the side of the cylinder when a potential (electrical pressure) was applied to the cathode, Plucker re- ferred to as "Cathode Rays". In 1869 another man named Hittorf discovered that by placing an electrode in front of the cathode a shadow was produced on the side of the tube when a current was applied to the cathode. Later Sir William Crookes made the electrode in front of the cathode in the shape of a Maltese Cross which produced a shadow of its shape on the side of the ANODE ACCELERATES tube when a potential was applied to •ELECTRONS the cathode. What did all these experi- ments show? Namely two things: that there was an electrical flow between COLD CATHODE PRODUCING ELECTRON 'BEAM' the two electrodes; and that by placing a third element in the path of the electrons a shadow could be obtained. of the selenium, affect the strength of signals transmitted. At the receiver the In 1897 Professor Karl Ferdinand signals could then be changed back Braun, Austrian How was the C.R.T. again into a picture of the scene trans- improved ? physicist at mitted. In practice, selenium was too Strasburg Uni- sluggish to be effective. Later other versity, improved Sir William Crookes, photo-sensitive materials were used, cathode ray tube (C.R.T.) in several which actually produced currents when ways. He placed at the thick end of subjected to variations in light. Nip- the tube (opposite the cathode) a kow's experiments were confined to a mica screen coated with phosphorus, telegraph line. Later television, like which would fluoresce when bom- radio, was to be transmitted through barded with electrons emitted from the ether. cathode. The screen was protected by a glass front through which one could Over a hundred years ago Julius see the fluorescent glow. Another Plucker, an scientist, Ryan, found that by putting What is a Cathode electromagnetic coils around the neck Ray Tube ? American, thought of using of the tube; by means of varying the an evacuated glass cylinder with an current flowing through the coils; and electrode at each end, a cathode nega- by varying the position of the coil tively charged, and an anode (or plate) itself, he was able to spotlight the beam 41 VERTED IMA( \

Baird was the first man to broadcast the Derby in 1931—the picture was very wobbly. on the screen to a far greater degree was President of the Rontgen Society, of accuracy than could Braun. The he suggested that the transmitting tube C.R.T. was further improved by a man should be evacuated of all air, and that named Wehnelt, who by coating the the scene to be transmitted should be cathode with an electron emitting oxide exposed to a mosaic screen of rubi- and by heating it, produced a much dium, which would produce the neces- brighter spot on the screen. In 1907, sary charges for transmission of the a Russian, Boris Rosing, built a tele- object televised. It was many years vision set for display purposes. He used later before this excellent theory was a C.R.T. for the receiver and a mirror put into practice. type of scanner for the transmitter. But the whole system lacked amplification In 1923, the celebrated John Logie for practical use and once again the Baird appeared selenium, the key to the early experi- Who first broadcast on the scene An the Derby by ... ments, was found to be too sluggish. television? intrepid inventor, The following year, 1908, an English- and a tenacious man by the name of A. A. Campbell Scot, we see him in his small room at Swinton, who was an electrical Hastings using odd bits of wireless and engineer, put forward the idea that a other materials, together with the head C.R.T. should be used at the trans- of a ventriloquist's dummy as his mitter as well as at the receiving end of model. He favoured the rotating disc transmission. Later, in 1911 when he as a means of scanning, and he was the 42 is receiving signals from the trans- mitter. It all happens so quickly that all you see is the completed picture. As we read, as far back as in 1908, A. A. Campbell Swinton had advo- cated using cathode ray tubes in both transmitter and receiver. In America, Vladimir Zworykin had patented an electronic camera tube, called the Iconoscope, which was part way to achieving this idea of Swinton's. In 1932, Sir Isaac Schoenberg, Director of Research of the Electrical and Musical DEFLECTOR COILS v TO AMPLIFIER Industries (E.M.I.), with his team pro- duced the Emitron Mark I camera tube. In March 1934 it was agreed to form a company between Marconi and A section of a modern television camera to show how it E.M.I, and it became known as works. Marconi-E.M.I. Co. Ltd. They pro- duced television cameras using the first man to actually broadcast for the electronic gun as compared with Baird's B.B.C. experimental programmes in mechanical screening. 1929 and 1930. He was the first man Very briefly, the television camera to broadcast the Derby in 1931 and in works on the principle that the scene 1932 with improved pictures on a televised is exposed, through the 8" x 10" screen scanning 30 lines. This camera lens, to the screen consisting couldn't have been anything like as of a mosaic of photo-electric silver- clear as the 405 lines and the 625 caesium cells, which takes up a charge lines used today. when subjected to the varying degrees of light from the scene to be televised. If you look at your present screen These charges are released for trans- you will see mission by being subjected to a stream How is the picture of electrons from the electronic gun formed ? the picture is composed of a which scans continuously the mosaic number of lines, created by a single screen, in the same way that the screen spot of light which is travelling so fast of your receiver is screened. that it gives the appearance of lines, which in turn are scarcely visible if they In the same year, 1934, a select are properly controlled to give a com- committee was plete picture. That single spot of light Why was Marconi's set up by the system superior to is created by electrons being shot from Baird's? Postmaster the cathode of your tube, which in turn General, with 43 Lord Selsdon as chairman. Their pur- of the Radio Exhibition at Olympia. pose was to report on the quality of the Later that year, in November, the television systems being developed at Postmaster General opened Alexandra that time. In 1935 it was found that Palace Station, and in February the Baird's system used 240 lines with 25 following year he announced that the pictures a second, whereas the Mar- Marconi-E.M.I. system had been coni-E.M.I. used 405 lines, with 25 recommended for public use. Although pictures a second, and that the pictures closed for the duration of the war, produced by the latter were superior to television became popular soon after- the former. In August 1936, both wards and more recently colour tele- systems broadcasted on the occasion vision as well.

Many satellites have been launched, and even when they have stopped transmitting they remain in orbit around the earth. Communication by Satellite

In 1945 an Englishman named Arthur satellites would in effect be in a con- C. Clarke put tinuous position over the earth and Who thought Of a forward the idea messages sent to them would be communications P , , received and re-transmitted by the of satellite? manned satel- operators aboard to other earth stations lites • for com- within range of the satellites. munication, advocating that they be placed in synchronous orbits, synchro- An American scientist, John Robin- nizing, that is, with the movement of son Pierce, suggested ten years later the earth. In this way the artificial using unmanned satellites, passive and 44 There have been four different Intelsat satellites launched. From left to right—Intelsat II; Intelsat IV; Intelsat I; and Intelsat III. active, circulating in synchronous and achieved by means of a giant rocket, random orbits. which in different stages, usually three, carries the satellite up to the required It was found that the micro-wave height and position and releases it to frequencies used be sent in orbit around the earth. Once Why use an in orbit it is controlled from base and artificial satellite ? by the early satellites were can be used for sending radio, tele- more stable than long distance com- vision or telephone signals to any part munication by short wave ground of the globe in range and suitably stations. A satellite acting as a relay equipped with special aerials to receive station far above the ionosphere such signals. covers a far greater area and a greater distance than any method yet used. Its There are, as already stated, passive signals penetrating the ionosphere are and active satel- unaffected by its changes, which would What is the p, n difference .betwee . n lites. Passive affect lower frequency signals. Once active and passive satellites, Such as the satellite is launched, this form of satellites? Echo I launched communication, used internationally, by the United can be cheaper and more reliable than States in 1960 and Echo II launched in other systems. 1963, had no means of re-transmitting Before the satellite can commence signals, but owing to their surfaces, operating it has to be launched thou- reflected the signals back to earth. Not sands of miles into space. This is having any working parts these satel- 45 lites could not be controlled from base, satellite in range, and so on to prevent after launching. The advantages of break in transmission and reception. passive satellites are that there is little A satellite can only serve one third of to go wrong with them, until they cease the earth's surface at any one time. to function altogether; they do not For this reason transmitting and re- have to be energized as active satellites ceiving stations have to point their are, and they are able to reflect signals aerials directly at the satellite as in the from a number of ground stations case of the Post Office ground station simultaneously. They do, however, at Goonhilly Downs in Cornwall. have to be big. Echo I was a 100 ft. Synchronous orbiting satellites, how- diameter plastic balloon thinly coated ever, have the advantage of following with metal. After a time it became the earth's rotation with a single orbit, punctured and torn by particles in and in effect remaining in a similar space. One of the principal dis- spot over the earth's surface. To achieve advantages of passive satellites is that this they have to be launched into a they require much stronger transmit- very high orbit over 22,000 miles above ting signals and very sensitive receivers the earth's surface. Three such satel- on earth to operate satisfactorily. lites suitably placed can connect Active satellites, on the other hand, practically any two places in the world. carry both receiver and transmitter. They receive signals, sent from specially Let us now consider individual satel- beamed aerials on earth, and then lites. It would amplify them and transmit them back Which important take t0Q jong tQ satellites have been r again to other earth stations. To do this launched? enumerate them they receive their power from solar all, but let us cells exposed to and energized from the consider a few and their earth com- sun. municating stations. The American Telephone and Telegraph Company Before considering any more individual working in conjunction with N.A.S.A. artificial satellites (National Aeronautics and Space How do satellites j us consider orbit the earth ? Administration) produced the world- the orbits in famous Telstar satellite, which was which they operate. Satellites travelling launched in July 1962, being placed at random orbits are usually used in in orbit by a Delta rocket. Many conjunction with other satellites. As the television programmes were exchanged name suggests, they orbit at random, between the U.S. and Europe both in independent of the world's rotation. colour and black and white. It was Spaced apart, the satellites are followed also used for telephone calls either way by earth stations, receivers and trans- and for relaying photoprints. Damage mitters, until one satellite passes over by radiation to its transistor circuits the horizon, then the transmitting was detected by earth control, and it beam is switched to the following went silent on 21 February 1963. 46 Telstar II was launched on 7 May 1963, sortium), the last named organization with improved design to resist radia- being a collection of 81 (to date) tion. The first commercial satellite different nations owning the satellites Early Bird was launched in April 1965. which now cover the globe with a Remaining in one spot over the Atlantic commercial communication system by it carried 240 telephone channels and satellite. The first successful Intelsat II could also broadcast television between was launched and placed over the the United States and Europe, and more Pacific Ocean on 11 January 1967 recently, with two other satellites, one and connected North America with in the Indian Ocean and one in the Australia and the Far East. Pacific, we are able to receive television Intelsat III was launched over the signals from Australia in Great Britain. Atlantic in September 1968, and an- Russia orbited her first communications other successful Intelsat III was satellite, Molniya, in 1965. launched over the Pacific in May 1969 which later was moved in June of that Following Early Bird, which was year to over the Indian Ocean. also known as The 25 January 1971 saw the When were the Intelsat I, were launching at Cape Kennedy of the Intelsat satellites launched? a series of other biggest in the Intelsat satellites world, at that date, Intelsat IV. Built launched by N.A.S.A. for Comsat by Hughes Aircraft in America, (Communication Satellite Corporation) measuring 17| ft. high by 7ft. 9in. on behalf of Intelsat (International in diameter, this most sophisticated Satellite Con- communications satellite was made to

The biggest communications satellite yet launched is Intelsat IV. 47 Two earth stations: left—Moree Ground Station in Australia; right—Warksworth in New Zealand. cope with 9,000 two-way telephone Glossary conversations or to transmit 12 simultaneous colour television pro- Series Direct connection, as grammes or a combination of these at opposed to parallel. the same time. It possesses six antennae Series—tw*—•mi— Parallel wwww— (aerials), two global for receiving, two Cohere Stick together. global for transmitting and two for Condenser A component capable of spot beam transmitting. storing electricity. In the last week of February 1972 Conductor Substances which will the third Intelsat IV communications carry electrical current, satellite televised the historic visit of such as metal, wire, etc. President Nixon to the People's Current The flow of electricity Republic of China, and people of the measured in amperes. Western world were able to see his Frequency Number of cycles of meeting with Chairman Mao. As the alternating current per number of satellites increases so second. does the number of earth ground Insulators Substances which will stations all over the world from prevent the flow of elec- America to Japan. tric current. By exploring outer space and by Voltage Electromagnetic force, making use of the knowledge attained measured in volts. man can now communicate with his Watts Unit of electric power. fellow man, both audibly and visually, Kilo-watt (1,000 watts). in split seconds, from one end of the Wavelength Distance between the world to the other by means of arti- crest of one wave and ficial satellite, television and radio. In another. Shown by the this way we are nearer to those in symbol A. foreign lands than ever before. 48 NEW! A collector's binder to hold HOW AND WHYL, This new How and Why collector's binder holds twelve titles: a wonderful way to build your own reference library! It is^available from the publishers of How and Why books for £2.00 Supplies are limited so send for yours now.

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These books answer the questions most often asked about science, nature and history. They are presented in a clear, readable style, and contain many colourful and instructive illustra- tions. Readers will want to explore each of these fascinating subjects and collect these volumes as an authentic, ready-reference, basic library.

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