For these fluids, use NBR seals code N. For fluids HFDR type. The solenoid valve in the explosion-proof version is in turn ATEX certified and as such it is identified with its own tag, wich carries the relative. ATEX marking.
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The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. It was of enormous value in finding and retrieving hundreds of relevant articles from journals published throughout the twentieth century.
In addition, many articles are published on the Internet alone. I would also like to thank: The enthusiasts who run the many online museums to show their collections. Wikipedia images for many useful pictures.
The librarians of Cambridge University Library for leading me through some of the byways of their collections. Clive Horwood for his encouragement, Maury Solomon particularly when it became necessary to split an overlong book, and Elizabet Cabrera.
Jim and Rachael Wilkie for turning the manuscript into a book with the cover design and editing. Last, but certainly not least, I want to thank my wife who has, without realizing it, taught me so much about history. Outside, a wire ran up to a Baden-Powell six-sided linen kite which he and his assistant George Kemp were only keeping aloft with difficulty.
They had already lost another kite and a balloon, and they were only using these because an antennae array at Cape Cod had blown down. On the other side of the Atlantic, above Poldhu cove in Cornwall, almost as far west in Britain as you can get without falling into the sea, was another, much larger collection of equipment.
A small power station generated 25 kW of electricity, and when a Morse key was pressed a huge arc leapt across a spark gap, dying away when the key was released. The signal thus generated was led to a set of wires held aloft by two 60 m towers. This arrangement replaced a much larger m—diameter inverted cone array which, again, had blown down.
At It was the Morse code for S that he had arranged to be transmitted from Poldhu. He passed the earpiece to Kemp who listened. He could hear it too. Twice more that day they heard the signal, but then the weather worsened and they had to stop. What they had achieved was to receive a wireless signal from the other side of the Atlantic, a feat that many experts thought was impossible. Basically they were right, but he had been lucky, as the particular range of frequencies generated by his transmitter would bounce off atmospheric layers and, hence, could be received way beyond the horizon.
In the event, he waited a few days before saying anything to the press. Later, he was to prove long-distance communication much more convincingly, and in the following decade or so the Marconi company built up a substantial business supplying wireless communication facilities, particularly to ships.
It might be thought that Marconi had mastered the technology for wireless communica- tion, but what he was using was very crude and it was only refinement and huge amounts of power that enabled it to work at all. It fact, what he was using was purely electrical, and a blind alley. What was needed for really satisfactory equipment was the means to enlarge or amplify signals and the ability both to generate and receive them in a very narrow fre- quency band.
In , J. Electronics is one of those words that everyone knows what is meant by it, but when it comes to a definition, it slips through your fingers. The Electronics Revolution is about how we went from absolutely nothing to the abun- dance of electronic items that we regard as normal today. For communication we expect mobile phones, and the Internet. Now it seems that every man, woman and child has a mobile phone in their pocket or handbag. Something that was the plaything of the few is now the norm for everyone.
Modern business could not function without the instant com- munication of email. For entertainment, there are radios and TVs, and music on tap for our personal use.
We so expect instant TV from anywhere in the world that it is difficult to realize that it was as late as before the first live TV pictures flashed across the Atlantic, and they could only be maintained for a matter of minutes. We become involved in wars or disasters in other countries in ways that would have been incomprehensible to our forefathers. For work and play, there is computing. Home computers have become ubiquitous. Offices are full of computers, and yet more computers control whole organizations.
But computers can also be in the form of microprocessors buried in appliances such as wash- ing machines or central heating boilers. There is a long trail of successes, and some failures, but with one thing leading to another, often in an apparently unrelated way: wartime radar to microwave ovens, and moonshots to worldwide live TV. The intention is to follow these links to show how it all fits together.
For example, without radio and TV our modern democracy is barely imaginable. So often this impact of technology has been largely ignored. How was all this achieved? There is often a great confusion between these, with the words being used interchangeably, but there is a key difference.
Science is about ideas in the natural world, while engineering is about their exploitation into technology useful to humankind. Even once the science is in place, in order to introduce a major technological change there are three distinct phases: invention, development and exploitation. Introduction 3 The fundamental science comes first.
James Clerk Maxwell predicted the existence of electromagnetic waves, and Heinrich Hertz proved he was right—that was the science. Others, such as Eduoard Branly who developed the coherer detector, or Oliver Lodge who demonstrated a wireless communication system which could ring a bell remotely, were the inventors. At this point, though there was interesting knowledge, there was still nothing useful.
It required a Marconi to come along and bring it all together. Besides being rather unkind about his abilities, it completely misses the point. What he was able to do was to take these various inventions and develop them into a system. He could then take this and exploit it to allow communica- tion from a ship to the shore or vice versa. He had produced something useful to people. Though most of the knowledge of the relevant physical laws of electricity was under- stood before the end of the nineteenth century, much concerning electronics had still to be learned.
In some cases, it took some time to understand the devices that had been invented. With solid state physics, mostly investigated in the first half of the twentieth century, it was the search to understand that led to the invention of transistors. The fantastic bounty brought by integrated circuits and microcomputers, though, was more a matter of technol- ogy than of science.
To follow the story, we need to look at the people who made things happen. Some of these people will be well known, but others may well be surprising. There are many unsung heroes who made vital contributions but received little credit because someone else was better at the publicity. Some names are known, such as Tim Berners-Lee for the World Wide Web, and John Logie Baird for television though his contribution was not quite what it is often assumed to be.
People such as Isaac Schoenberg and Alan Blumlein, who really got the system going, are barely remembered, and what of Boris Rosing who always seems to be at the back of all the successful television developments? And who has heard of Nobel prizewinner Charles Kao whose determination gave us fiber optics on which modern communications depend? When the time was ripe often a number of people come up with much the same idea.
Simultaneous invention is quite common: Jack Kilby and Robert Noyce came up with integrated circuits at much the same time, though the concept was already known. What matters here is the turning of ideas into something useful. At the end of all these developments we have reached a state where electronics have permeated every aspect of our lives. As so often, these things were summed up by a TV advert. An amusing one for Renault electric cars imagined a world where common items were powered by tiny engines and not by electricity.
The star was a handheld card machine which had to be refuelled to work. In one way it made its point, but in another completely missed it.
Without electricity there would be no electronics. Without electronics there would be no computers. Without computers credit cards would not exist so there would be no need for a card machine. In any case, the system depends on wireless and other elec- tronic communication, so the handheld unit would not exist. The record of people and organizations, when the technology on which they depend becomes obsolete, is not good.
He was lucky in that he employed J. Ambrose Fleming as a consultant and so, by chance, his company came to hold one of the key patents. He had the foresight to employ Henry Round to develop the necessary devices, so the company smoothly made the transition. The great arc transmitters were phased out, and electronics took over. NOTE 1. Thomas A. Edison One of the areas that particularly attracted the interest of experimenters in the nineteenth century was the behavior of evacuated glass tubes when excited by electricity.
As the char- acteristics change with the amount of gas remaining in the equipment, the whole experi- ment depended on how well the air could be removed.
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