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The development of electronic communication in the early 19th century

The vacuum tube era Theoretical and experimental studies of electricity during the 18th and 19th centuries led to the development of the first electrical machines and the beginning of the widespread use of electricity. The history of electronics began to evolve separately from that of electricity late in the 19th century with the identification of the electron by the English physicist Sir Joseph John Thomson and the measurement of its electric charge by the American physicist Robert A. Edison had observed a bluish glow in some of his early lightbulbs under certain conditions and found that a current would flow from one electrode in the lamp to another if the second one anode were made positively charged with respect to the first cathode.

Work by Thomson and his students and by the English engineer John Ambrose Fleming revealed that this so-called Edison effect was the result of the emission of electrons from the cathode, the hot filament in the lamp. The motion of the electrons to the anode, a metal plate, constituted an electric current that would not exist if the anode were negatively charged. This discovery provided impetus for the development of electron tubes, including an improved X-ray tube by the American engineer William D.

The detection of a radio signal, which is a very high-frequency alternating current ACrequires that the signal be rectified; i. These devices were undependable, lacked sufficient sensitivity, and required constant adjustment of the whisker-to-crystal contact to produce the desired result. The fact that crystal rectifiers worked at all encouraged scientists to continue studying them and gradually to obtain the fundamental understanding of the electrical properties of semiconducting materials necessary to permit the invention of the transistor.

In 1906 Lee De Forestan American engineer, developed a type of vacuum tube that was capable of amplifying radio signals.

De Forest added a grid of fine wire between the cathode and anode of the two-electrode thermionic valve constructed by Fleming. The new device, which De Forest dubbed the Audion patented in 1907was thus a three-electrode vacuum tube. In operation, the anode in such a vacuum tube is given a positive potential positively biased with respect to the cathode, while the grid is negatively biased. A large negative bias on the grid prevents any electrons emitted from the cathode from reaching the anode; however, because the grid is largely open space, a less negative bias permits some electrons to pass through it and reach the anode.

Small the development of electronic communication in the early 19th century in the grid potential can thus control large amounts of anode current. The vacuum tube permitted the development of radio broadcasting, long-distance telephony, television, and the first electronic digital computers.

These early electronic computers were, in fact, the largest vacuum-tube systems ever built. The special requirements of the many different applications of vacuum tubes led to numerous improvements, enabling them to handle large amounts of power, operate at very high frequencies, have greater than average reliability, or be made very compact the size of a thimble.

The cathode-ray tubeoriginally developed for displaying electrical waveforms on a screen for engineering measurements, evolved into the television picture tube. Such tubes operate by forming the electrons emitted from the cathode into a thin beam that impinges on a fluorescent screen at the end of the tube.

The screen emits light that can be viewed from outside the tube. Deflecting the electron beam causes patterns of light to be produced on the screen, creating the desired optical images. Notwithstanding the remarkable success of solid-state devices in most electronic applications, there are certain specialized functions that only vacuum tubes can perform. These usually involve operation at extremes of power or frequency.

Vacuum tubes are fragile and ultimately wear out in service. Failure occurs in normal usage either from the effects of repeated heating and cooling as equipment is switched on and off thermal fatiguewhich ultimately causes a physical fracture in some part of the interior structure of the tube, or from degradation of the properties of the cathode by residual gases in the tube.

These shortcomings motivated scientists at Bell Laboratories to seek an alternative to the vacuum tube and led to the development of the transistor. The semiconductor revolution Invention of the transistor The invention of the transistor in 1947 by John BardeenWalter H. Brattainand William B. Shockley of the Bell research staff provided the first of a series of new devices with remarkable potential for expanding the utility of electronic equipment see photograph.

Transistors, along with such subsequent developments as integrated circuitsare made of crystalline solid materials called semiconductorswhich have electrical properties that can be varied over an extremely wide range by the addition of minuscule quantities of other elements. The availability of two kinds of charge carriers in semiconductors is a valuable property exploited in many electronic devices made of such materials. Early transistors were produced using germanium as the semiconductor material, because methods of purifying it to the required degree had been developed during and shortly after World War II.

Because the electrical properties of semiconductors are extremely sensitive to the slightest trace of certain other elements, only about one part per billion of such elements can be tolerated in material to be used for making semiconductor devices. During the late 1950s, research on the purification of silicon succeeded in producing material suitable for semiconductor devices, and new devices made of silicon were manufactured from about 1960.

Silicon quickly became the preferred raw material, because it is much more abundant than germanium and thus less expensive. In addition, silicon retains its semiconducting properties at higher temperatures than does germanium. There was one other important property of silicon, not appreciated at the time but crucial to the development of low-cost transistors and integrated circuits: This film is utilized as a mask to permit the desired impurities that modify the electrical properties of silicon to be introduced into it during manufacture of semiconductor devices.

The mask pattern, formed by a photolithographic process, permits the creation of tiny transistors and other electronic components in the silicon. Integrated circuits By 1960 vacuum tubes were rapidly being supplanted by transistors, because the latter had become less expensive, did not burn out in service, and were much smaller and more reliable.

Computers employed hundreds of thousands of transistors each. This fact, together with the need for compact, lightweight electronic missile-guidance systems, led to the invention of the integrated circuit IC independently by Jack Kilby of Texas Instruments Incorporated in 1958 and by Jean Hoerni and Robert Noyce of Fairchild Semiconductor Corporation in 1959.

Kilby is usually credited with having developed the concept of integrating device and the development of electronic communication in the early 19th century elements onto a single silicon chip, while Noyce is given credit for having conceived the method for integrating the separate elements.

Early ICs contained about 10 individual components on a silicon chip 3 mm 0. By 1970 the number was up to 1,000 on a chip of the same size at no increase in cost. Late in the following year the first microprocessor was introduced.

The globalization of electronic news in the 19th century

This type of large-scale IC was developed by a team at Intel Corporationthe same company that also introduced the memory IC in 1971. The stage was now set for the computerization of small electronic equipment. Until the microprocessor appeared on the scene, computers were essentially discrete pieces of equipment used primarily for data processing and scientific calculations.

They ranged in size from minicomputerscomparable in dimensions to a small filing cabinet, to mainframe systems that could fill a large room. The microprocessor enabled computer engineers to develop microcomputers —systems about the size of a lunch box or smaller but with enough computing power to perform many kinds of business, industrial, and scientific tasks.

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Such systems made it possible to control a host of small instruments or devices e. The very existence of computer hardware inside such devices is not apparent to the user. The large demand for microprocessors generated by these initial applications led to high-volume production and a dramatic reduction in cost. This in turn promoted the use of the devices in many other applications—for example, in household appliances and automobiles, for which electronic controls had previously been too expensive to consider.

Continued advances in IC technology gave rise to very large-scale integration VLSIwhich substantially increased the circuit density of microprocessors. These technological advances, coupled with further cost reductions stemming from improved manufacturing methods, made feasible the mass production of personal computers for use in offices, schools, and homes.

By the mid-1980s inexpensive microprocessors had stimulated computerization of an enormous variety of consumer products. Common examples included programmable microwave ovens and thermostats, clothes washers and dryers, self-tuning television sets and self-focusing cameras, videocassette recorders and video games, telephones and answering machines, musical instruments, watches, and security systems.

Microelectronics also came to the fore in business, industrygovernment, and other sectors. Microprocessor-based equipment proliferated, ranging from automatic teller machines ATMs and point-of-sale terminals in retail stores to automated factory assembly systems and office workstations. By mid-1986 memory ICs with a capacity of 262,144 bits binary digits were available. In fact, Gordon E. Mooreone of the founders of Intel, observed as early as 1965 that the complexity of ICs was approximately doubling every 18—24 months, which was still the case in 2000.

History of telecommunication

Moore's lawIn 1965 Gordon E. Moore observed that the number of transistors on a computer chip was doubling about every 18—24 months. Compound semiconductor materials Many semiconductor materials other than silicon and germanium exist, and they have different useful properties.

Silicon carbide is a compound semiconductor, the only one composed of two elements from column IV of the periodic table. It is particularly suited for making devices for specialized high-temperature applications. Other compounds formed by combining elements from column III of the periodic table—such as aluminum, gallium, and indium—with elements from column V—such as phosphorus, arsenic, and antimony—are of particular interest.

These so-called III-V compounds are used to make semiconductor devices the development of electronic communication in the early 19th century emit light efficiently or that operate at exceptionally high frequencies. A remarkable characteristic of these compounds is that they can, in effect, be mixed together. One can produce gallium arsenide or substitute aluminum for some of the gallium or also substitute phosphorus for some of the arsenic.

When this is done, the electrical and optical properties of the material are subtly changed in a continuous fashion in proportion to the amount of aluminum or phosphorus used. Except for silicon carbidethese compounds have the same crystal structure. This makes possible the gradation of compositionand thus the properties, of the semiconductor material within one continuous crystalline body.

Modern material-processing techniques allow these compositional changes to be controlled accurately on an atomic scale. These characteristics are exploited in making semiconductor lasers that produce light of any given wavelength within a considerable range. Such lasers are used, for example, in compact disc players and as light sources for optical fibre communication.

Digital electronics Computers understand only two numbers, 0 and 1, and do all their arithmetic operations in this binary mode. Many electrical and electronic devices have two states: A light switch is a familiar example, as are vacuum tubes and transistors. Because computers have been a major application for integrated circuits from their beginning, digital integrated circuits have become commonplace.

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It has thus become easy to design electronic systems that use digital language to control their functions and to communicate with other systems. A major advantage in using digital methods is that the accuracy of a stream of digital signals can be verified, and, if necessary, errors can be corrected. An example is the sound from a phonograph recordwhich always contains some extraneous sound from the surface of the recording groove even when the record is new.

The noise becomes more pronounced with wear. Contrast this with the the development of electronic communication in the early 19th century from a digital compact disc recording. No sound is heard that was not present in the recording studio.

The disc and the player contain error-correcting features that remove any incorrect pulses perhaps arising from dust on the disc from the information as it is read from the disc. As electronic systems become more complex, it is essential that errors produced by noise be removed; otherwise, the systems may malfunction. Many electronic systems are required to operate in electrically noisy environmentssuch as in an automobile.

The only practical way to assure immunity from noise is to make such a system operate digitally. In principle it is possible to correct for any arbitrary number of errors, but in practice this may not be possible.

The amount of extra information that must be handled to correct for large rates of error reduces the capacity of the system to handle the desired information, and so trade-offs are necessary. A consequence of the veritable explosion in the number and kinds of electronic systems has been a sharp growth in the electrical noise level of the environment. Any electrical system generates some noise, and all electronic systems are to some degree susceptible to disturbance from noise. The noise may be conducted along wires connected to the system, or it may be radiated through the air.