Volt
The volt is the derived unit for electric potential, electric potential difference, electromotive force. It is named after the Italian physicist Alessandro Volta. One volt is defined as the difference in electric potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points, it is equal to the potential difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it, it can be expressed in terms of SI base units as V = potential energy charge = J C = kg ⋅ m 2 A ⋅ s 3. It can be expressed as amperes times ohms, watts per ampere, or joules per coulomb, equivalent to electronvolts per elementary charge: V = A ⋅ Ω = W A = J C = eV e; the "conventional" volt, V90, defined in 1987 by the 18th General Conference on Weights and Measures and in use from 1990, is implemented using the Josephson effect for exact frequency-to-voltage conversion, combined with the caesium frequency standard.
For the Josephson constant, KJ = 2e/h, the "conventional" value KJ-90 is used: K J-90 = 0.4835979 GHz μ V. This standard is realized using a series-connected array of several thousand or tens of thousands of junctions, excited by microwave signals between 10 and 80 GHz. Empirically, several experiments have shown that the method is independent of device design, measurement setup, etc. and no correction terms are required in a practical implementation. In the water-flow analogy, sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping and a capacitor/inductor could be likened to a "U" shaped pipe where a higher water level on one side could store energy temporarily; the relationship between voltage and current is defined by Ohm's law. Ohm's Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems.
The voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. See Galvanic cell § Cell voltage. Cells can be combined in series for multiples of that voltage, or additional circuitry added to adjust the voltage to a different level. Mechanical generators can be constructed to any voltage in a range of feasibility. Nominal voltages of familiar sources: Nerve cell resting potential: ~75 mV Single-cell, rechargeable NiMH or NiCd battery: 1.2 V Single-cell, non-rechargeable: alkaline battery: 1.5 V. Some antique vehicles use 6.3 volts. Electric vehicle battery: 400 V when charged Household mains electricity AC: 100 V in Japan 120 V in North America, 230 V in Europe, Asia and Australia Rapid transit third rail: 600–750 V High-speed train overhead power lines: 25 kV at 50 Hz, but see the List of railway electrification systems and 25 kV at 60 Hz for exceptions. High-voltage electric power transmission lines: 110 kV and up Lightning: Varies often around 100 MV.
In 1800, as the result of a professional disagreement over the galvanic response advocated by Luigi Galvani, Alessandro Volta developed the so-called voltaic pile, a forerunner of the battery, which produced a steady electric current. Volta had determined that the most effective pair of dissimilar metals to produce electricity was zinc and silver. In 1861, Latimer Clark and Sir Charles Bright coined the name "volt" for the unit of resistance. By 1873, the British Association for the Advancement of Science had defined the volt and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission, approved the volt as the unit for electromotive force, they made the volt equal to 108 cgs units of voltage
Incandescent light bulb
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated to such a high temperature that it glows with visible light. The filament is protected from oxidation with a glass or fused quartz bulb, filled with inert gas or a vacuum. In a halogen lamp, filament evaporation is slowed by a chemical process that redeposits metal vapor onto the filament, thereby extending its life; the light bulb is supplied with electric current by feed-through terminals or wires embedded in the glass. Most bulbs are used in a socket which provides electrical connections. Incandescent bulbs are manufactured in a wide range of sizes, light output, voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, work well on either alternating current or direct current; as a result, the incandescent bulb is used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, flashlights, for decorative and advertising lighting.
Incandescent bulbs are much less efficient than other types of electric lighting. The remaining energy is converted into heat; the luminous efficacy of a typical incandescent bulb for 120 V operation is 16 lumens per watt, compared with 60 lm/W for a compact fluorescent bulb or 150 lm/W for some white LED lamps. Some applications of the incandescent bulb deliberately use the heat generated by the filament; such applications include incubators, brooding boxes for poultry, heat lights for reptile tanks, infrared heating for industrial heating and drying processes, lava lamps, the Easy-Bake Oven toy. Incandescent bulbs have short lifetimes compared with other types of lighting. Incandescent bulbs have been replaced in many applications by other types of electric light, such as fluorescent lamps, compact fluorescent lamps, cold cathode fluorescent lamps, high-intensity discharge lamps, light-emitting diode lamps; some jurisdictions, such as the European Union, China and United States, are in the process of phasing out the use of incandescent light bulbs while others, including Colombia, Cuba and Brazil, have prohibited them already.
In addressing the question of who invented the incandescent lamp, historians Robert Friedel and Paul Israel list 22 inventors of incandescent lamps prior to Joseph Swan and Thomas Edison. They conclude that Edison's version was able to outstrip the others because of a combination of three factors: an effective incandescent material, a higher vacuum than others were able to achieve and a high resistance that made power distribution from a centralized source economically viable. Historian Thomas Hughes has attributed Edison's success to his development of an entire, integrated system of electric lighting; the lamp was a small component in his system of electric lighting, no more critical to its effective functioning than the Edison Jumbo generator, the Edison main and feeder, the parallel-distribution system. Other inventors with generators and incandescent lamps, with comparable ingenuity and excellence, have long been forgotten because their creators did not preside over their introduction in a system of lighting.
In 1761 Ebenezer Kinnersley demonstrated heating a wire to incandescence. In 1802, Humphry Davy used what he described as "a battery of immense size", consisting of 2,000 cells housed in the basement of the Royal Institution of Great Britain, to create an incandescent light by passing the current through a thin strip of platinum, chosen because the metal had an high melting point, it was not bright enough nor did it last long enough to be practical, but it was the precedent behind the efforts of scores of experimenters over the next 75 years. Over the first three-quarters of the 19th century, many experimenters worked with various combinations of platinum or iridium wires, carbon rods, evacuated or semi-evacuated enclosures. Many of these devices were demonstrated and some were patented. In 1835, James Bowman Lindsay demonstrated a constant electric light at a public meeting in Dundee, Scotland, he stated that he could "read a book at a distance of one and a half feet". Lindsay, a lecturer at the Watt Institution in Dundee, Scotland, at the time, had developed a light, not combustible, created no smoke or smell and was less expensive to produce than Davy's platinum-dependent bulb.
However, having perfected the device to his own satisfaction, he turned to the problem of wireless telegraphy and did not develop the electric light any further. His claims are not well documented, although he is credited in Challoner et al. with being the inventor of the "Incandescent Light Bulb". In 1838, Belgian lithographer Marcellin Jobard invented an incandescent light bulb with a vacuum atmosphere using a carbon filament. In 1840, British scientist Warren de la Rue enclosed a coiled platinum filament in a vacuum tube and passed an electric current through it; the design was based on the concept that the high melting point of platinum would allow it to operate at high temperatures and that the evacuated chamber would contain fewer gas molecules to react with the platinum, improving its longevity. Although a workable design, the cost of the platinum made it impractical for commercial use. In 1841, Frederick de Moleyns of England was granted the first patent for an incandescent lamp, with a design using platinum wires contained within a vacuum
Dekatron
In electronics, a Dekatron is a gas-filled decade counting tube. Dekatrons were used in computers and other counting-related products during the 1950s and 1960s. "Dekatron," now a generic trademark, was the brand name used by Ericsson Telephones Limited, of Beeston, Nottingham. The dekatron was useful for computing and frequency-dividing purposes because one complete revolution of the neon dot in a dekatron means 10 pulses on the guide electrode, a signal can be derived from one of the ten cathodes in a dekatron to send a pulse for another counting stage. Dekatrons have a maximum input frequency in the high kilohertz range – 100 kHz is fast, 1 MHz is around the maximum possible; these frequencies are obtained in hydrogen-filled fast dekatrons. Dekatrons filled with inert gas are inherently more stable and have a longer life, but their counting frequency is limited to 10 kHz. Internal designs vary by the model and manufacturer, but a dekatron has ten cathodes and one or two guide electrodes plus a common anode.
The cathodes are arranged in a circle with a guide electrode between each cathode. When the guide electrode is pulsed properly, the neon gas will activate near the guide pins "jump" to the next cathode. Pulsing the guide electrodes will cause the neon dot to move from cathode to cathode. Hydrogen dekatrons require high voltages ranging from 400 to 600 volts on the anode for proper operation; when a dekatron is first powered up, a glowing dot appears at a random cathode. The color of the dot depends on the type of gas, in the tube. Neon-filled tubes display a red-orange dot. Counter dekatrons have only one carry/borrow cathode wired to its own socket pin for multistage cascading and the remaining nine cathodes tied together to another pin. Counter/Selector dekatrons have each cathode wired to its own pin. Selectors allow for monitoring the status of each cathode or to divide-by-n with the proper reset circuitry; this kind of versatility made such dekatrons useful for numerical division in early calculators.
Dekatrons come in various physical sizes, ranging from smaller than a 7-pin miniature vacuum tube to as large as an octal base tube. While most dekatrons are decimal counters, models were made to count in base-5 and base-12 for specific applications; the dekatron fell out of practical use when transistor-based counters became reliable and affordable. Today, dekatrons are used by electronic hobbyists in simple "spinners" that run off the mains frequency or as a numeric indicator for homemade clocks. Sumlock ANITA calculator — The world's first desktop electronic calculators, which used Dekatrons. WITCH — Early British relay-based computer that used Dekatrons. Ericsson Telephones computing tubes designation system Special Quality gas-filled tubes designation system Jennings, Thomas ‘Tom’, Nixie Indicators and Decimal Counting Tubes, WPS. "Vacuum Tubes, Cold-Cathode Switching Tubes & Dekatron Counter Tubes", Calculator Electronics, Vintage Calculators Web Museum. "Spinner for European mains", Electric stuff, UK.
"Spinner for American mains", Electronix & more, archived from the original on 2007-06-07. "Dekatrons", Tube tester. "Comprehensive dekatron table", Decade counter, Vintage Technology Association. Sandor, Nagy, "A Dekatron tube display", Asimov Teka, EU
Burroughs Corporation
The Burroughs Corporation was a major American manufacturer of business equipment. The company was founded in 1886 as the American Arithmometer Company, after the 1986 merger with Sperry UNIVAC was renamed Unisys; the company's history paralleled many of the major developments in computing. At its start, it produced mechanical adding machines, moved into programmable ledgers and computers, it was one of the largest producers of mainframe computers in the world producing related equipment including typewriters and printers. In 1886, the American Arithmometer Company was established in St. Louis, Missouri to produce and sell an adding machine invented by William Seward Burroughs. In 1904, six years after Burroughs' death, the company moved to Detroit and changed its name to the Burroughs Adding Machine Company, it was soon the biggest adding machine company in America. The adding machine range began with the basic, hand-cranked P100, only capable of adding; the design included some revolutionary features, foremost of, the dashpot.
The P200 offered a subtraction capability and the P300 provided a means of keeping 2 separate totals. The P400 provided a moveable carriage, the P600 and top-of-the-range P612 offered some limited programmability based upon the position of the carriage; the range was further extended by the inclusion of the "J" series which provided a single finger calculation facility, the "c" series of both manual and electrical assisted comptometers. In the late 1960s, the Burroughs sponsored. Burroughs developed a range of adding machines with different capabilities increasing in their capabilities. A revolutionary adding machine was the Sensimatic, able to perform many business functions semi-automatically, it had a moving programmable carriage. It could store 9, 18 or 27 balances during the ledger posting operations and worked with a mechanical adder named a Crossfooter; the Sensimatic developed into the Sensitronic which could store balances on a magnetic stripe, part of the ledger card. This balance was read into the accumulator.
The Sensitronic was followed by the E1000, E2000, E3000, E4000, E6000 and the E8000, which were computer systems supporting card reader/punches and a line printer. Burroughs was selling more than adding machines, including typewriters, but the biggest shift in company history came in 1953: the Burroughs Adding Machine Company was renamed the Burroughs Corporation and began moving into computer products for banking institutions. This move began with Burroughs' purchase in June 1956, of the ElectroData Corporation in Pasadena, California, a spinoff of the Consolidated Engineering Corporation which had designed test instruments and had a cooperative relationship with Caltech in Pasadena. ElectroData had built the Datatron 205 and was working on the Datatron 220; the first major computer product that came from this marriage was the B205 tube computer. In the late 1960s the L and TC series range was produced which had a golf ball printer and in the beginning a 1K disk memory; these were popular as branch terminals to the B5500/6500/6700 systems, sold well in the banking sector, where they were connected to non-Burroughs mainframes.
In conjunction with these products, Burroughs manufactured an extensive range of cheque processing equipment attached as terminals to a larger system such as a B2700 or B1700. Burroughs was one of the nine major United States computer companies in the 1960s, with IBM the largest, Honeywell, NCR Corporation, Control Data Corporation, General Electric, Digital Equipment Corporation, RCA and Sperry Rand. In terms of sales, Burroughs was always a distant second to IBM. In fact, IBM's market share was so much larger than all of the others that this group was referred to as "IBM and the Seven Dwarfs." By 1972 when GE and RCA were no longer in the mainframe business, the remaining five companies behind IBM became known as the BUNCH, an acronym based on their initials. At the same time, Burroughs was much a competitor. Like IBM, Burroughs tried to supply a complete line of products for its customers, including Burroughs-designed printers, disk drives, tape drives, computer printing paper, typewriter ribbons.
In the 1950s, Burroughs worked with the Federal Reserve Bank on the development and computer processing of magnetic ink character recognition for the processing of bank cheques. Burroughs made special MICR/OCR sorter/readers which attached to their medium systems line of computers and this entrenched the company in the computer side of the banking industry; the Burroughs Corporation developed three innovative architectures, based on the design philosophy of "language-directed design". Their machine instruction sets favored one or many high level programming languages, such as ALGOL, COBOL or FORTRAN. All three architectures were considered mainframe class machines: The Burroughs large systems machines started with the B5000 in 1961; the B5500 came a few years when large rotating disks replaced drums as the main external memory media. These B5000 Series systems used the world's first virtual memory multi-programming operating system, they were followed by the B6500/B6700 in the 1960s, the B7700 in the mid 1970s, the A series in the 1980s.
The underlying architecture of these machines is similar and continues today as the Unisys ClearPath MCP line of computers: stack machines designed to be programmed in an extended Algol 60. Their operating systems, called MCP (Master Contr
Calculator
An electronic calculator is a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-sized devices became available in the 1970s after the Intel 4004, the first microprocessor, was developed by Intel for the Japanese calculator company Busicom, they became used within the petroleum industry. Modern electronic calculators vary from cheap, give-away, credit-card-sized models to sturdy desktop models with built-in printers, they became popular in the mid-1970s as the incorporation of integrated circuits reduced their size and cost. By the end of that decade, prices had dropped to the point where a basic calculator was affordable to most and they became common in schools. Computer operating systems as far back as early Unix have included interactive calculator programs such as dc and hoc, calculator functions are included in all personal digital assistant type devices, the exceptions being a few dedicated address book and dictionary devices.
In addition to general purpose calculators, there are those designed for specific markets. For example, there are scientific calculators which include trigonometric and statistical calculations; some calculators have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higher-dimensional Euclidean space; as of 2016, basic calculators cost little. In 1986, calculators still represented an estimated 41% of the world's general-purpose hardware capacity to compute information. By 2007, this had diminished to less than 0.05%. Electronic calculators contain a keyboard with buttons for arithmetical operations. Most basic calculators assign operation on each button. Calculators have liquid-crystal displays as output in place of historical light-emitting diode displays and vacuum fluorescent displays. Large-sized figures are used to improve readability. Various symbols for function commands may be shown on the display. Fractions such as 1⁄3 are displayed as decimal approximations, for example rounded to 0.33333333.
Some fractions can be difficult to recognize in decimal form. Calculators have the ability to store numbers into computer memory. Basic calculators store only one number at a time; the variables can be used for constructing formulas. Some models have the ability to extend memory capacity to store more numbers. Power sources of calculators are: batteries, solar cells or mains electricity, turning on with a switch or button; some models have no turn-off button but they provide some way to put off. Crank-powered calculators were common in the early computer era; the following keys are common to most pocket calculators. While the arrangement of the digits is standard, the positions of other keys vary from model to model. In general, a basic electronic calculator consists of the following components: Power source Keypad – consists of keys used to input numbers and function commands Display panel – displays input numbers and results. Liquid-crystal displays, vacuum fluorescent displays, light-emitting diode displays use seven segments to represent each digit in a basic calculator.
Advanced calculators may use dot matrix displays. A printing calculator, in addition to a display panel, has a printing unit that prints results in ink onto a roll of paper, using a printing mechanism. Processor chip. Clock rate of a processor chip refers to the frequency at which the central processing unit is running, it is used as an indicator of the processor's speed, is measured in clock cycles per second or the SI unit hertz. For basic calculators, the speed can vary from a few hundred hertz to the kilohertz range. A basic explanation as to how calculations are performed in a simple four-function calculator: To perform the calculation 25 + 9, one presses keys in the following sequence on most calculators: 2 5 + 9 =; when 2 5 is entered, it is picked up by the scanning unit. This "pushes" the first number out into the Y register.
Multimeter
A multimeter or a multitester known as a VOM, is an electronic measuring instrument that combines several measurement functions in one unit. A typical multimeter can measure voltage and resistance. Analog multimeters uses a microammeter with a moving pointer to display readings. Digital multimeters have a numeric display, may show a graphical bar representing the measured value. Digital multimeters are now far more common due to their cost and precision, but analog multimeters are still preferable in some cases, for example when monitoring a varying value. A multimeter can be a hand-held device useful for basic fault finding and field service work, or a bench instrument which can measure to a high degree of accuracy. Multimeters are available in a wide range of prices. Cheap multimeters can cost less than US$10, while laboratory-grade models with certified calibration can cost more than US$5,000; the first moving-pointer current-detecting device was the galvanometer in 1820. These were used to measure resistance and voltage by using a Wheatstone bridge, comparing the unknown quantity to a reference voltage or resistance.
While useful in the lab, the devices were slow and impractical in the field. These galvanometers were delicate; the D'Arsonval–Weston meter movement uses a moving coil which carries a pointer and rotates on pivots or a taut band ligament. The coil rotates in a permanent magnetic field and is restrained by fine spiral springs which serve to carry current into the moving coil, it gives proportional measurement rather than just detection, deflection is independent of the orientation of the meter. Instead of balancing a bridge, values could be directly read off the instrument's scale, which made measurement quick and easy; the basic moving coil meter is suitable only for direct current measurements in the range of 10 μA to 100 mA. It is adapted to read heavier currents by using shunts or to read voltage using series resistances known as multipliers. To read alternating currents or voltages, a rectifier is needed. One of the earliest suitable rectifiers was the copper oxide rectifier developed and manufactured by Union Switch & Signal Company, Pennsylvania part of Westinghouse Brake and Signal Company, from 1927.
Multimeters were invented in the early 1920s as radio receivers and other vacuum tube electronic devices became more common. The invention of the first multimeter is attributed to British Post Office engineer, Donald Macadie, who became dissatisfied with the need to carry many separate instruments required for maintenance of telecommunications circuits. Macadie invented an instrument which could measure amperes and ohms, so the multifunctional meter was named Avometer; the meter comprised a moving coil meter and precision resistors, switches and sockets to select the range. The Automatic Coil Winder and Electrical Equipment Company, founded in 1923, was set up to manufacture the Avometer and a coil winding machine designed and patented by MacAdie. Although a shareholder of ACWEECO, Mr MacAdie continued to work for the Post Office until his retirement in 1933, his son, Hugh S. MacAdie, became Technical Director; the first AVO was put on sale in 1923, many of its features remained unaltered through to the last Model 8.
Any meter will load the circuit under test to some extent. For example, a multimeter using a moving coil movement with full-scale deflection current of 50 microamps, the highest sensitivity available, must draw at least 50 μA from the circuit under test for the meter to reach the top end of its scale; this may load a high-impedance circuit so much as to affect the circuit, thereby giving a low reading. The full-scale deflection current may be expressed in terms of "ohms per volt"; the ohms per volt figure is called the "sensitivity" of the instrument. Thus a meter with a 50 μA movement will have a "sensitivity" of 20,000 Ω/V. "Per volt" refers to the fact that the impedance the meter presents to the circuit under test will be 20,000 Ω multiplied by the full-scale voltage to which the meter is set. For example, if the meter is set to a range of 300 V full scale, the meter's impedance will be 6 MΩ. 20,000 Ω/V is the best sensitivity available for typical analog multimeters that lack internal amplifiers.
For meters that do have internal amplifiers, the input impedance is fixed by the amplifier circuit. The first Avometer had a sensitivity of 60 Ω/V, three direct current ranges, three direct voltage ranges, a 10,000 Ω resistance range. An improved version of 1927 increased this to 166.6 Ω/V movement. A "Universal" version having additional alternating current and alternating voltage ranges was offered from 1933 and in 1936 the dual-sensitivity Avometer Model 7 offered 500 and 100 Ω/V. Between the mid 1930s until the 1950s, 1,000 Ω/V became a de facto standard of sensitivity for radio work and this figure was quoted on service sheets. However, some manufacturers such as Simpson and Weston, all in the USA, produced 20,000 Ω/V VOMs before the Second World War and some of these were exported. After 1945–46, 20,000 Ω/V became the expected standard for electronics, but some makers offered more sensitive instruments. For industrial and other "heavy-current" use low sensitivity multimeters continued to be produced and these were considered more robust than the more sensitive types.
High-quality analog multimeters continue to be made by several manufacturers, including Chauvin Arnoux, Gossen Me
Electronics
Electronics comprises the physics, engineering and applications that deal with the emission and control of electrons in vacuum and matter. The identification of the electron in 1897, along with the invention of the vacuum tube, which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age. Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, diodes, integrated circuits and sensors, associated passive electrical components, interconnection technologies. Electronic devices contain circuitry consisting or of active semiconductors supplemented with passive elements; the nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible. Electronics is used in information processing, telecommunication, signal processing; the ability of electronic devices to act as switches makes digital information-processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, other varied forms of communication infrastructure complete circuit functionality and transform the mixed electronic components into a regular working system, called an electronic system.
An electronic system may be a component of a standalone device. Electrical and electromechanical science and technology deals with the generation, switching and conversion of electrical energy to and from other energy forms; this distinction started around 1906 with the invention by Lee De Forest of the triode, which made electrical amplification of weak radio signals and audio signals possible with a non-mechanical device. Until 1950 this field was called "radio technology" because its principal application was the design and theory of radio transmitters and vacuum tubes; as of 2018 most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid-state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering; this article focuses on engineering aspects of electronics. Digital electronics Analogue electronics Microelectronics Circuit design Integrated circuits Power electronics Optoelectronics Semiconductor devices Embedded systems An electronic component is any physical entity in an electronic system used to affect the electrons or their associated fields in a manner consistent with the intended function of the electronic system.
Components are intended to be connected together by being soldered to a printed circuit board, to create an electronic circuit with a particular function. Components may be packaged singly, or in more complex groups as integrated circuits; some common electronic components are capacitors, resistors, transistors, etc. Components are categorized as active or passive. Vacuum tubes were among the earliest electronic components, they were solely responsible for the electronics revolution of the first half of the twentieth century. They allowed for vastly more complicated systems and gave us radio, phonographs, long-distance telephony and much more, they played a leading role in the field of microwave and high power transmission as well as television receivers until the middle of the 1980s. Since that time, solid-state devices have all but taken over. Vacuum tubes are still used in some specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment, guitar amplifiers and some microwave devices.
In April 1955, the IBM 608 was the first IBM product to use transistor circuits without any vacuum tubes and is believed to be the first all-transistorized calculator to be manufactured for the commercial market. The 608 contained more than 3,000 germanium transistors. Thomas J. Watson Jr. ordered all future IBM products to use transistors in their design. From that time on transistors were exclusively used for computer logic and peripherals. Circuits and components can be divided into two groups: digital. A particular device may consist of circuitry that has a mix of the two types. Most analog electronic appliances, such as radio receivers, are constructed from combinations of a few types of basic circuits. Analog circuits use a continuous range of voltage or current as opposed to discrete levels as in digital circuits; the number of different analog circuits so far devised is huge because a'circuit' can be defined as anything from a single component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many non-linear effects are used in analog circuits such as mixers, etc. Good examples of analog circuits include vacuum tube and transistor amplifiers, operational amplifiers and oscillators. One finds modern circuits that are analog; these days analog circuitry may use digital or microprocessor techniques to improve performance. This type of circuit is called "mixed signal" rather than analog or digital. Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear and non-linear
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