Marconis progress in business

Marconi was more than a resourceful inventor and a master of publicity. He was a shrewd businessman as well. After patenting his invention in July 1896, he turned his attention to business matters. With the aid of his cousin, who had good contacts both in scientific and financial circles, he managed to found The Wireless Telegraph and Signal Co. Ltd. (it changed its name to Marconi's Wireless Telegraph Co. Ltd. two years later) in July 1897, with capital of 100000. He received 75000 for his...

The invention of the transistor

By the end of the Second World War some people strongly believed that the time for solid state amplifiers had arrived. During the war lots of advances were made in producing purer crystals for microwave rectifiers, so the technological problems no longer looked so daunting. And the motivation was there too. Vacuum tubes were examined and were found wanting. They were clumsy, expensive and unreliable. And progress wasn't very fast either. It had been a good thirty years since the invention of...

The laser appears

1 An indication of the interest of the US Air Force at the time is that they were willing to support research for shorter millimetre waves at the French electronics company CSF while de Gaulle was delivering his anti-American tirades. 2 The new unit appearing here is T for Tera meaning lo12Hz IOOOOOOOOO OOO Hz I million MHz 1000 GHz. Advances usually come in small steps. A swimmer might be celebrated if he improves the world record from (say) 3 minutes 25.2 seconds to 3 minutes 24.3 seconds...

Optical fibres for communications

For Reeves the advent of the laser came as an unexpected boon. His men were already running along the right track when a bandwagon suddenly appeared. They jumped upon it without losing any time while the rest of the world was not even aware that there were any bandwagons on the move. Reeves and his co-workers looked at various guiding structures the hollow metal tube already mentioned an array of lenses (called confocal waveguides because the light in them was focussed and defocussed as it...

The Second Industrial Revolution has arrived

Let me summarize again the main steps, as I see them, in the development that brought about the modern age. To my mind it all started with William Thomson's calculations on the operation of the trans-Atlantic telegraph cable. It was the first time that higher mathematics had been used to solve an urgent engineering problem. It was the beginning of a trend that said that engineering intuition was fine but that it cannot always be relied on. Engineers had to accept that the solution of some...

The principles of radio

Hertz's apparatus was shown in Fig. 6.3. It worked. It was the first one that worked nonetheless it is not the best for explaining the underlying principles. From a more modern viewpoint, an apparatus that will radiate electromagnetic waves may be represented schematically by the block diagram of Fig. 6.4. Obviously, there must be a source of power you can't get something out of nothing. The next element is an oscillator. Its function is to produce a fast-varying current as shown in Fig....

Box 121 Dielectric waveguides

The phenomenon of light refraction has probably been known since the start of human civilization. Put a stick in water and it appears as if it is broken. It is a consequence of the fact that when light moves from a medium of lower refractive index (like air) into a medium of higher refractive index (like water) the rays will change direction at the boundary as shown in Fig. Bi2.l(a). When light is incident Fig. B12.1 (a) A ray of light refracts when moving from a medium...

Why optics

Of all the electromagnetic spectrum the part most studied in the course of human history is light. The main reason has been the early availability of powerful light sources ('Let there be light', Day 1) supplemented five days later by a marvellously effective broadband light detector. Ever since, the subject has been a playground of philosophers and physicists, of theoreticians and of men of practical bent. The amount of knowledge accumulated by the 1950s was formidable. By that time there were...

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...

The young Marconi

The story of the invention of wireless has been told in countless books for experts, for the layman and even for children. It is a story of success. A young Italian hardly out of school brings to England the fruits of his research. He takes the country by storm, becomes rich and famous, and receives the Nobel Prize, the highest scientific accolade, at the age The name of the young Italian was Guglielmo Marconi. He had a young and beautiful socialite for a mother and a rather morose country...

Satellite communications

Microwave links can span continents but cannot offer communications across the oceans. In principle, it would have been possible to lay a microwave waveguide under the ocean, but it did not even become a practical proposition on land, let alone under the sea. Was there a third microwave alternative Yes. It was proposed in 1945, not by an expert in telecommunication techniques but by a renowned writer of science fiction, Arthur C. Clarke. This is hardly surprising considering that satellite...

The CR limit and periodic loading

Sound declines as it moves away from its source. That much is obvious. What may be added here is that when the electric current is modulated by the incident sound, that modulation will decline too. At the transmitting end the current as a function of time looks like that shown in Fig. 5.17(a) but at the receiving end the modulation may be much THE CR LIMIT AND PERIODIC LOADING Current THE CR LIMIT AND PERIODIC LOADING Current Fig. 5.17 (a) The modulated electric current. (b) At the modulation...

Waveguides

The advantage of microwave links was that lots of channels could be transmitted without needing to lay cables in the ground. Does that mean that guiding structures (microwave cables are usually referred to as waveguides or, more generally, as guiding structures) were entirely unsuitable for microwave communications No, they were not. At one time the prospects looked exciting. Waveguides are made of hollow metal tubes which may have rectangular or circular cross-sections, as shown in Fig. 9.6....

Frequency division multiplexing

2 Many people find it difficult to imagine that a large number of conversations may coexist on a single line without any effect upon each other. It may be worth pointing out that exactly the same thing happens with radio broadcasting. All the various programmes arrive simultaneously to our radio set without affecting each other (well, sometimes they do ) and the selection of the right station takes place in our own set by turning a knob. Time division multiplexing was introduced in order to...

The principles of a triode amplifier

A schematic diagram of a triode is shown in Fig. B6.2. The third electrode between the cathode and the anode consists of a wire grid which hardly affects the motion of the electrons from the cathode to the anode when there is no voltage on it. However, a small positive voltage on the grid gives great encouragement to the flow of electrons. The current from cathode to anode increases significantly. A negative voltage applied to the grid discourages the flow of electrons, i.e. the current...

Principles of operation and a brief technical history

Are the basic principles as simple as those needed to understand the telegraph Not quite. To understand the telegraph all one needs to know is that electrical circuits may be switched ON and OFF and, in addition, one must be able to distinguish the symbols 1 and o from each other. In order to understand the basic principles underlying the operation of the telephone somewhat more is needed. One should, to start with, have some idea of the physical properties of sound. What are they By the middle...

Early attempts

The chances of sending a picture by telegraph very much improved with the invention of the electrical telegraph. It would have been, for Fig. 15.2 A possible solution for sending a fax by semaphore. Fig. 15.3 Schematic representation of the fax machine invented by Alexander Bain. Mechanism to lower or raise message block 1 There is an entry under Bain, Alexander in most encyclopaedias. He was a Scotsman who lived in the nineteenth century. Alas, the Alexander Bain of the encyclopaedias was a...

The transistor goes west

The first transistors were made of a semiconductor called germanium. It had the disadvantage that it could not work at high temperatures. Silicon, another semiconductor, was much more suitable for higher temperatures which inevitably occur in many devices but its technology was more demanding. Bell Laboratories were of course involved in trying to make silicon technology work. By this time Shockley was not there. He had a desk job at the Pentagon as an eminent civilian scientist but he was not...