The communications revolution

hapter The Second World War gave an enormous push to all things techno-

EIGHT logical but the main beneficiary was not communications: rather it was aircraft propulsion, rockets, radar and of course the not-quite-so-peaceful side of nuclear engineering. Gigantic advances gave rise to gigantic confidence, best characterized by the American maxim: the difficult we do right away, the impossible takes a little longer.

Of greatest relevance to the advance of communications was the work on radar. After all, what radar does is to radiate in a narrow direction a pulse of electromagnetic waves which is reflected by the target and, from the time taken for the pulse to come back, the distance of the target from the radar set may be determined. The emphasis was on electromagnetic waves. The same waves that had been used for communications since the end of the last century. Hence the advances made during the war in producing electromagnetic waves could be easily translated to use those same waves for communications. The frequency range used by radar was in the microwave region (see Fig. 6.2 for the electromagnetic spectrum) hence microwave links for communications were a simple continuation of the work done during the war.

A second advance was also due to radar. The devices which detected the reflected electromagnetic waves were made of semiconducting crystals. A semiconductor is neither a good nor a bad conductor of electricity. But if it conducts electricity at all then it must contain some electrons. If it contains electrons then one might be able to regulate the flow of those electrons. If one can regulate the flow, as in a vacuum tube, then it might be possible to produce an amplifier out of a semiconducting material. This was indeed the view in Bell Laboratories, the research laboratories of AT&T. They got going immediately after the war and by Christmas 1948 they produced the transistor, the most important electronic device of the century. Further development in this field brought the integrated circuit and the microprocessor which led to the proliferation of personal computers.

A third advance was due to the development of rocket technology and to the imagination of Arthur C. Clarke, the science fiction writer. He envisaged a number of geostationary satellites (i.e. satellites which orbit at the same speed as the Earth rotates hence appearing stationary to an earthling) which relay information from one end of the Earth to the other.

The fourth advance, and probably the greatest advance, was the birth of information theory. This is concerned with the relationship between information and noise: to be precise, how noise will corrupt information. Its main tenet is just amazing. It took me a long time to absorb it. It maintains that if we do our best and we are not too greedy (i.e. we are happy not to exceed a certain rate when sending information) then it is possible to ensure that the information can be transferred without a single error.

The fifth advance is often referred to as the digital revolution but it should perhaps be called the digital evolution, because it came more in the form of a stream gradually expanding into a broad river than a torrent sweeping away everything. The idea was actually patented a little before the war but did not reach the market place until the 1960s. What's the good of it? It turns out that by putting information into digital form it can be processed much better. Not without a single error, that sounds a little utopian, but with present techniques error rates of less than one in a billion can be achieved routinely.

The sixth advance is optical communications, the seeds of which were planted some considerable time after the war. It brought together two elements: lasers and optical fibres. It enabled engineers to introduce light into a thin (about as thin as a human hair) strand of glass and guide it all the way to the other side of the Atlantic. The information to be transmitted, say the complete text and pictures of the Encyclopaedia Britannica, could be put on the light beam in London and the whole lot would reach New York before you could say 'Jack Robinson'.

The seventh advance enabled computers to talk to each other. First it was just a question of how to teach them to communicate with each other, but then it burgeoned into a network and later into a network of networks, until in the end it brought us electronic mail and the World Wide Web.

Seven is a magical number. There are usually seven wonders of this or that. While admitting that other classifications are possible I would settle on the seven post-war advances as mentioned above. But of course communications had a great impact upon other fields as well, particularly on economics: how wealth is generated and how we spend our money.

As the highways and the airways of the world get more and more crowded, contacts between human beings tend increasingly to move away from direct physical contact to seeing and hearing each other on screens. The exponential increase in the number of communications devices seems to go on unabated. We are spending greater and greater portions of our income on sending and acquiring information.

The administration and running of communications networks has also undergone major changes. It used to be thought of as a natural monopoly, i.e. the consumer got the best deal if it was run by a single organization, a company like AT&T in the US or various state agencies in most other parts of the world. This belief was undermined practically

1 Actually, not all. Greece, Ireland, Portugal and Spain received a short respite.

2 For example, the travelling wave tube, the most ingenious of all microwave amplifiers, was invented by Rudi Kompfner and brought to perfection by John Pierce.

3 He received the Nobel Prize for it in 1971.

simultaneously around the middle of the 1980s in the two English-speaking countries, the US and the UK, by the divestiture of the Bell System in the former and by the privatization of British Telecom in the latter. All the world has been following that initiative ever since. The latest blow to state ownership was a directive of the European Union in 1997 instructing all the member countries to start dismantling their monopolies from January 1998.1

Finally, about genius in the post-war world. Are there still great heroes in the field of communications? There are, although not in the sense that they have become household names. Nor would there be a clear consensus about who they are. It probably depends on where you live and whom you meet. I don't think there would be any dispute about the first three: they are William Shockley, John Bardeen and Walter Brattain, the inventors of the transistor. They were before my time, anyway. As for the rest of my heroes, I met them all. Alec Reeves, who took out the first patent on Pulse Code Modulation and who had telecommunications in his blood, was my boss while I worked at Standard Telecommunications Laboratories. All the others turned up at one time or another in Oxford. The man who made the greatest advance was Claude Shannon, who single-handedly founded Information Theory. Two of my heroes, Rudi Kompfner and John Pierce, may be seen in Fig. 9.9. They were both Directors of Bell Research Laboratories at the time. Among many other feats2 they were responsible for putting satellite communications into practice. In this photograph Rudi is in his characteristic pose. He seems puzzled. But within a minute or so he is going to advance an explanation nobody ever thought of. A man whose impact on communications is still to come was Dennis Gabor. He invented holography.3 It will be due to him if one day our moving images grow out of our boxes and appear in thin air in their full three-dimensional pomp.

I have ended up with seven heroes. A sign of the times is the American dominance. Four of the seven were born in the US (of the other three one was born in England, one in Austria, and one in Hungary) and even the Austrian-born did most of his work in the US. Will the American dominance continue? For the time being, yes. Where will technical leadership go next? Japan? China? My guess is good old Europe. Having been punished for falling under the spell of two particularly nasty 'isms', Nazism and Communism, the Old Continent will reclaim and regain its birthright in the next two or three decades.

0 0

Post a comment