Interview Questions-Basics of Electronics and Communication Engg

extremely pure ( referred as intrinsic) semiconductor for the purpose of changing or modulating its electrical properties.
The impurities are dependent on the type of semiconductor. Lightly and moderately doped semiconductors are referred to as extrinsic.
Semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as degenerate.

such as silicon and germanium or compound such as gallium arsenide.
Silicon is the most used semiconductor for discrete devices and integrated circuits. One of the prominent German scientists wrote in an article about silicon that this era is the silicon era since silicon impacted and still affecting the modern civilization development very much..

into the circuit. They only let current through in one direction. The diodes in the distortion pedal are what make the distortion. Diode-clipping distortion is what this is called! There is a certain way to connect diodes. It is pretty straight forward. There is always some sort of line on a diode (except for LED's) but on regular diodes there is always a line

the forward direction

A Zener diode is a diode is a diode which allows current to flow in the forward direction in the same manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is above a certain value known as the breakdown voltage, "Zener knee voltage", "Zener voltage", "avalanche point", or "peak inverse voltage".
The device was named after Clarence ZenerThe device was named after Clarence Zener, who discovered this electrical property. Strictly speaking, a Zener diode is one in which the reverse breakdown is due to electron quantum tunnellingThe device was named after Clarence Zener, who discovered this electrical property. Strictly speaking, a Zener diode is one in which the reverse breakdown is due to electron quantum tunnelling under high electric field strength—the Zener effectThe device was named after Clarence Zener, who discovered this electrical property. Strictly speaking, a Zener diode is one in which the reverse breakdown is due to electron quantum tunnelling under high electric field strength—the Zener effect. However, many diodes described as "Zener" diodes rely instead on avalanche breakdownThe device was named after Clarence Zener, who discovered this electrical property. Strictly speaking, a Zener diode is one in which the reverse breakdown is due to electron quantum tunnelling under high electric field strength—the Zener effect. However, many diodes described as "Zener" diodes rely instead on avalanche breakdown as the mechanism. Both types are used with the Zener effect predominating under 5.6 V and avalanche breakdown above.

two transistor types.

(extrinsic) semiconductor materials, either P-N-P or N-P-N.
Each layer forming the transistor has a specific name, and each layer is provided with a wire contact for connection to a circuit.

is an integrated circuit (chip) used in a variety of timer is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.

A.C. Converters belong to the category of Switched Mode Power Supplies (SMPS).
Various types of voltage regulators, used in Linear Power Supplies (LPS), fall in the category of dissipative regulator, as they have  a voltage control element usually transistor or zener diode which dissipates power equal to the voltage difference between an unregulated input voltage and a fixed supply voltage multiplied by the current flowing through it.
The switching regulator acts as a continuously variable power converter and hence its efficiency is barely affected by the voltage difference .

15 to 50 kHz using an active device like the BJT, power MOSFET or SCR and the converter transformer. Here the size of the ferrite core reduces inversely with the frequency.
The lower limit is around 5 kHz for silent operation and an upper limit of 50 kHz to limit the losses in the choke and in active switching elements.
The transformed wave form is rectified and filtered. A sample of the output voltage is used as the feedback signal for the drive circuit for the switching transistor to achieve regulation.

or close to the CPU can operate faster than the much larger main memory. Most CPUs since the 1980s have used one or more caches, and modern high-end embedded, desktop and server microprocessors may have as many as half a dozen, each specialized for a specific function. Examples of caches with a specific function are the D-cache and I-cache (data cache and instruction cache).
Translation lookaside buffer Main article: Translation lookaside buffer
A memory management unitA memory management unit (MMU) that fetches page table entries from main memory has a specialized cache, used for recording the results of virtual addressA memory management unit (MMU) that fetches page table entries from main memory has a specialized cache, used for recording the results of virtual address to physical addressA memory management unit (MMU) that fetches page table entries from main memory has a specialized cache, used for recording the results of virtual address to physical address translations. This specialized cache is called a translation lookaside bufferA memory management unit (MMU) that fetches page table entries from main memory has a specialized cache, used for recording the results of virtual address to physical address translations. This specialized cache is called a translation lookaside buffer (TLB]
Disk cache:
Page cache
While CPU caches are generally managed entirely by hardware, a variety of software manages other caches. The page cacheWhile CPU caches are generally managed entirely by hardware, a variety of software manages other caches. The page cache in main memoryWhile CPU caches are generally managed entirely by hardware, a variety of software manages other caches. The page cache in main memory, which is an example of disk cache, is managed by the operating system kernel.

referred to as "disk cache", its main functions are to write sequencing and read pre fetching. Repeated cache hits are relatively rare, due to the small size of the buffer in comparison to the drive's capacity. However, high-end disk controllersWhile the hard drive's hardware disk buffer is sometimes misleadingly referred to as "disk cache", its main functions are to write sequencing and read pre fetching. Repeated cache hits are relatively rare, due to the small size of the buffer in comparison to the drive's capacity. However, high-end disk controllers often have their own on-board cache of hard disk data blocks.
Finally, a fast local hard disk can also cache information held on even slower data storage devices, such as remote servers (web cacheFinally, a fast local hard disk can also cache information held on even slower data storage devices, such as remote servers (web cache) or local tape drivesFinally, a fast local hard disk can also cache information held on even slower data storage devices, such as remote servers (web cache) or local tape drives or optical jukeboxesFinally, a fast local hard disk can also cache information held on even slower data storage devices, such as remote servers (web cache) or local tape drives or optical jukeboxes. Such a scheme is the main concept of hierarchical storage management.
Web cache
Web browsersWeb browsers and web proxy serversWeb browsers and web proxy servers employ web caches to store previous responses from web serversWeb browsers and web proxy servers employ web caches to store previous responses from web servers, such as web pagesWeb browsers and web proxy servers employ web caches to store previous responses from web servers, such as web pages and imagesWeb browsers and web proxy servers employ web caches to store previous responses from web servers, such as web pages and images. Web caches reduce the amount of information that needs to be transmitted across the network, as information previously stored in the cache can often be re-used. This reduces bandwidth and processing requirements of the web server, and helps to improve responsiveness for users of the web.
Web browsers employ a built-in web cache, but some internet service providers or organizations also use a caching proxy server, which is a web cache that is shared among all users of that network.

by the satellite dish. A satellite dish is just a special kind of antenna designed to focus on a specific broadcast source.
The standard dish consists of a parabolic (bowl-shaped) surface and a central feed horn.
To transmit a signal, a controller sends it through the horn, and the dish focuses the signal into a relatively narrow beam.

refers to the part of the electromagnetic spectrum corresponding to radio frequencies refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz (or, equivalently, wavelengths longer than about 1 mm). Electromagnetic waves refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz (or, equivalently, wavelengths longer than about 1 mm). Electromagnetic waves in this frequency range, called radio waves refers to the part of the electromagnetic spectrum corresponding to radio frequencies – that is, frequencies lower than around 300 GHz (or, equivalently, wavelengths longer than about 1 mm). Electromagnetic waves in this frequency range, called radio waves, are used for radio communication and various other applications, such as heating.
The generation of radio waves is strictly regulated by the government in most countries, coordinated by an international standards body called the International Telecommunications Union (ITU). Different parts of the radio spectrum are allocated for different radio transmission technologies and applications. In some cases, parts of the radio spectrum is sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations).
Ranges of allocated frequencies are often referred to by their provisioned use (for example, cellular spectrum or television spectrum

ITU designation for the range of radio frequency) is the ITU designation for the range of radio frequency electromagnetic waves) is the ITU designation for the range of radio frequency electromagnetic waves from 30 MHz) is the ITU designation for the range of radio frequency electromagnetic waves from 30 MHz to 300 MHz) is the ITU designation for the range of radio frequency electromagnetic waves from 30 MHz to 300 MHz, with corresponding wavelengths of ten to one meters. Frequencies immediately below VHF are denoted high frequency) is the ITU designation for the range of radio frequency electromagnetic waves from 30 MHz to 300 MHz, with corresponding wavelengths of ten to one meters. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).
Common uses for VHF are FM radioCommon uses for VHF are FM radio broadcasting, televisionCommon uses for VHF are FM radio broadcasting, television broadcasting, land mobile stations (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modemsCommon uses for VHF are FM radio broadcasting, television broadcasting, land mobile stations (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur radioCommon uses for VHF are FM radio broadcasting, television broadcasting, land mobile stations (emergency, business, private use and military), long range data communication up to several tens of kilometres with radio modems, amateur radio, and marine communications.
Air traffic control Air traffic control communications and air navigation systems (e.g. VOR Air traffic control communications and air navigation systems (e.g. VOR, DME Air traffic control communications and air navigation systems (e.g. VOR, DME & ILS) work at distances of 100 kilometres or more to aircraft at cruising altitude.

are ways of broadcasting radio signals. Both transmit the information in the form of electromagnetic waves.
AM works by modulating (varying) the amplitude of the signal or carrier transmitted according to the information being sent, while the frequency remains constant.
This differs from FM technology in which information (sound) is encoded by varying the frequency of the wave and the amplitude is kept constant.

"carrier wave" is modulated in amplitude by the signal that is to be transmitted. The frequency and phase remain the same.
AM has poorer sound quality compared with FM, but is cheaper and can be transmitted over long distances. It has a lower bandwidth so it can have more stations available in any frequency range.AM radio ranges from 535 to 1705 KHz (OR) Up to 1200 bits per second.

in case of SSBSC AM carrier.

"carrier wave" is modulated in frequency by the signal that is to be transmitted.
The amplitude and phase remain the same.FM is less prone to interference than AM. However, FM signals are impacted by physical barriers.
FM has better sound quality due to higher bandwidth.FM radio ranges in a higher spectrum from 88 to 108 MHz. (OR) 1200 to 2400 bits per second.

modulating signal has to be converted and detected from corresponding variation in frequencies.(i.e. voltage to frequency and frequency to voltage

or S/N) is a measure used in science and engineering that compares the level of a desired signal) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. While SNR is commonly quoted for electrical signals, it can be applied to any form of signal (such as isotope levels in an ice core) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. While SNR is commonly quoted for electrical signals, it can be applied to any form of signal (such as isotope levels in an ice core or biochemical signaling between cells).
The signal-to-noise ratio, the bandwidthThe signal-to-noise ratio, the bandwidth, and the channel capacityThe signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channelThe signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channel are connected by the Shannon–Hartley theorem

a type of mobile phone is a type of mobile phone that connects to orbiting satellites is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites.
They provide similar functionality to terrestrial mobile telephones; voice They provide similar functionality to terrestrial mobile telephones; voice, short messaging service They provide similar functionality to terrestrial mobile telephones; voice, short messaging service and low-bandwidth internet access are supported through most systems.
Depending on the architecture of a particular system, coverage may include the entire Earth, or only specific regions.

include large, rugged, rack-mounted electronics, and a steerable microwave antenna on the mast that automatically tracks the overhead satellites.
Smaller installations using VoIP Smaller installations using VoIP over a two-way satellite broadband Smaller installations using VoIP over a two-way satellite broadband service such as BGAN Smaller installations using VoIP over a two-way satellite broadband service such as BGAN or VSAT Smaller installations using VoIP over a two-way satellite broadband service such as BGAN or VSAT bring the costs within the reach of leisure vessel owners. Internet service satellite phones have notoriously poor reception indoors, though it may be possible to get a consistent signal near a window or in the top floor of a building if the roof is sufficiently thin.
The phones have connectors for external antennas that can be installed in vehicles and buildings. The systems also allow for the use of repeaters, much like terrestrial mobile phone systems.

geosynchronous orbit is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of analemma.Orbit si about 36000 kms above a point of Earth.
A special case of geosynchronous satellite is the geostationary satellite, which has a geostationary orbit, which has a geostationary orbit – a circular geosynchronous orbit directly above the Earth's equator. Another type of geosynchronous orbit used by satellites is the Tundra elliptical orbit

permanently in the same area of the sky, as viewed from a particular location on Earth, and so permanently within view of a given ground station. Geostationary satellites have the special property of remaining permanently fixed in exactly the same position in the sky, meaning that ground-based antennas do not need to track them but can remain fixed in one direction.
Such satellites are often used for communication purposes; a geosynchronous network is a communication network based on communication with or through geosynchronous satellites.

safe security techniques to stop cybersecurity attacks.
These guides provide general outlines as well as specific techniques for implementing cybersecurity.
For certain standards, cybersecurity certification by an accredited body can be obtained. There are many advantages to obtaining certification including the ability to get cybersecurity insurance.

of an information signal to modify or improve it in some way. It is characterized by the representation of discrete time, discrete frequency, or other discrete domain signals by a sequence of numbers or symbols and the processing of these signals.
The goal of DSP is usually to measure, filter and/or compress continuous real-world analog signalsThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by samplingThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by sampling and then digitizing it using an analog-to-digital converterThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by sampling and then digitizing it using an analog-to-digital converter (ADC), which turns the analog signal into a stream of discrete digital values. Often, however, the required output signal is also analog, which requires a digital-to-analog converterThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by sampling and then digitizing it using an analog-to-digital converter (ADC), which turns the analog signal into a stream of discrete digital values. Often, however, the required output signal is also analog, which requires a digital-to-analog converter (DAC). Even if this process is more complex than analog processing and has a discrete value rangeThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by sampling and then digitizing it using an analog-to-digital converter (ADC), which turns the analog signal into a stream of discrete digital values. Often, however, the required output signal is also analog, which requires a digital-to-analog converter (DAC). Even if this process is more complex than analog processing and has a discrete value range, the application of computational power to signal processing allows for many advantages over analog processing in many applications, such as error detection and correctionThe goal of DSP is usually to measure, filter and/or compress continuous real-world analog signals. Usually, the first step is conversion of the signal from an analog to a digital form, by sampling and then digitizing it using an analog-to-digital converter (ADC), which turns the analog signal into a stream of discrete digital values. Often, however, the required output signal is also analog, which requires a digital-to-analog converter (DAC). Even if this process is more complex than analog processing and has a discrete value range, the application of computational power to signal processing allows for many advantages over analog processing in many applications, such as error detection and correction in transmission as well as data compression
Digital signal processing and analog signal processingDigital signal processing and analog signal processing are subfields of signal processingDigital signal processing and analog signal processing are subfields of signal processing. DSP applications include audioDigital signal processing and analog signal processing are subfields of signal processing. DSP applications include audio and speech signal processingDigital signal processing and analog signal processing are subfields of signal processing. DSP applications include audio and speech signal processing, sonar and radar signal processing, sensor array processing, spectral estimation, statistical signal processing, digital image processing

3D visualization.

Today’s complex products require a new design approach where multiple boards can be

the electrical and mechanical designs converge with little room for error. Detection at the prototype phase may be too late.

the use of computeris a broad term that means the use of computer technology to aid in the design, analysis, and manufacture of products.
Advanced CAx tools merge many different aspects of the product lifecycle managementAdvanced CAx tools merge many different aspects of the product lifecycle management (PLM), including design, finite element analysis (FEA), manufacturing, production planning, product
Computer-aided design (CAD)
Computer-aided engineering (CAE)
Computer-aided industrial design (CAID)
Computer-aided manufacturing (CAM)
Computer-aided requirements capture (CAR)
Computer-aided rule definition (CARD)
Computer-aided rule execution (CARE)
Computer-aided software engineering (CASE)
Computer-assisted surgery (CAS)
Computer-aided surgical simulation (CASS)
Computational fluid dynamics (CFD)

a PCB unroutable. Merging the packaging and PCB design into a single design solution significantly increases design quality.

package for design and presentation. It enables you to design and visualize in 3D, any scene you need for example: buildings, interiors, spaces or your products.
Flow helps you to present your work to others with screenshots, movies and a real-time virtual 3D walkthrough

image processing is the use of computer algorithms to perform image processingDigital image processing is the use of computer algorithms to perform image processing on digital imagesDigital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processingDigital image processing is the use of computer algorithms to perform image processing on digital images. As a subcategory or field of digital signal processing, digital image processing has many advantages over analog image processing.
It allows a much wider range of algorithms to be applied to the input data and can avoid problems such as the build-up of noise and signal distortion during processing. Since images are defined over two dimensions (perhaps more) digital image processing may be modeled in the form of multidimensional systems

recovering the exact positions of surface points. Moreover, it may be used to recover the motion pathways of designated reference points located on any moving object, on its components and in the immediately adjacent environment.
Photogrammetry may employ high-speed imaging and remote sensing Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields (see also sonar Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields (see also sonar, radar Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields (see also sonar, radar, lidar Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields (see also sonar, radar, lidar etc.). Photogrammetry feeds the measurements from remote sensing and the results of imagery analysis Photogrammetry may employ high-speed imaging and remote sensing in order to detect, measure and record complex 2-D and 3-D motion fields (see also sonar, radar, lidar etc.). Photogrammetry feeds the measurements from remote sensing and the results of imagery analysis into computational models in an attempt to successively estimate, with increasing accuracy, the actual, 3-D relative motions within the researched field.

that adapts to changing conditions with a crisp                                                outdoor-readable display and glove-capable                                                multi-touch.

have caught up on basic tube theory, and understand how a beam of electrons can be formed in a vacuum, we are well on our way to understanding how a KLYSTRON operates. If we have a device, which generates a beam of electrons, we notice that the electrons flow in a smooth steady stream at a particular uniform velocity. The area of the tube that the electron beam travels down is known as the DRIFT TUBE. If we insert, within the beam a grid, we can use this grid to control the beam. As we increase the positive potential on the grid, (assuming that we do not go over a certain potential which is less than the anode voltage), the electrons will be attracted to the grid, and by means of attraction, will be accellerated. On the other hand, should we decrease the potential, making it more negative, it will have the opposite effect on the beam, and try to slow down the electrons. We insert two grids, properly spaced for our experiment, and apply an alternating current source to the grids, such that as one grid swings positive, the other swings negative. This would mean that the electrons which are aproaching the positive going grid will be speeding up, as the ones aproaching the negative going grid will be slowing down. As the phase of the AC cycle changes 180 degrees, we have the same effect, only backwards. The result would be a sort of "slinky" effect, where the electron beam is interrupted, and moves along in bursts. This effect is known as VELOCITY MODULATION. In German, they say that electrons are moving in "Klystern". (Klyster is the German word for CLUSTER or BUNCH). Hence, the name Klystron. On the other end of our experimental Klystron, we have two more grids installed. The purpose of these are to "feel" the now pulsing beam of electrons as it passes by them on their way to the anode. Note that an electron does not have to come into direct contact with a wire in order to induce an electric current in it. All it has to do is pass near enough to generate the current in the wire via mutual inductance.

together with the Lorentz force are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents. They are named after the Scottish physicist/mathematician James Clerk Maxwell, who published an early form of those equations between 1861 and 1862.
The equations have two major variants. The "microscopic" set of Maxwell's equations uses total charge and total current, including the complicated charges and currents in materials at the atomic scale; it has universal applicability but may be unfeasible to calculate. The "macroscopic" set of Maxwell's equations defines two new auxiliary fields that describe large-scale behavior without having to consider these atomic scale details, but it requires the use of parameters characterizing the electromagnetic properties of the relevant materials.
The term "Maxwell's equations" is often used for other formsThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulationsThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-timeThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestlyThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with specialThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with special and general relativityThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with special and general relativity. In quantum mechanicsThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with special and general relativity. In quantum mechanics and analytical mechanicsThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with special and general relativity. In quantum mechanics and analytical mechanics, versions of Maxwell's equations based on the electricThe term "Maxwell's equations" is often used for other forms of Maxwell's equations. For example, space-time formulations are commonly used in high energy and gravitational physics. These formulations, defined on space-time rather than space and time separately, are manifestly compatible with special and general relativity. In quantum mechanics and analytical mechanics, versions of Maxwell's equations based on the electric and magnetic potentials are preferred.
Since the mid-20th century, it has been understood that Maxwell's equations are not exact laws of the universe, but are a classical approximation to the more accurate and fundamental theory of quantum electrodynamicsSince the mid-20th century, it has been understood that Maxwell's equations are not exact laws of the universe, but are a classical approximation to the more accurate and fundamental theory of quantum electrodynamics. In most cases, though, quantum deviations from Maxwell's equations are immeasurably small. Exceptions occur when the particle nature of light is important or for very strong electric fields.

are used in sophisticated, performance-critical components of advanced technology systems, such as traveling wave tubes (TWTs), klystrons, and magnetrons.
These are all used to amplify signals at microwave frequencies for high-performing radar, communications and electronic countermeasure systems.

parabolic antenna that transports the signal between a stationary transmitter is a particular type of parabolic antenna that transports the signal between a stationary transmitter or receiver is a particular type of parabolic antenna that transports the signal between a stationary transmitter or receiver and a movable dish by means of a beam waveguide. With a conventional "front fed" parabolic antenna, the antenna feed is a particular type of parabolic antenna that transports the signal between a stationary transmitter or receiver and a movable dish by means of a beam waveguide. With a conventional "front fed" parabolic antenna, the antenna feed, the small antenna that transmits or receives the radio waves reflected by the dish, is suspended at a focus, in front of the dish, and moves as the antenna is repositioned to track specific targets.

use the standard Internet protocol suite (TCP/IP) to link several billion devices worldwide. It is an international network of networks that consists of millions of private, public, academic, business, and government packet switched that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), the infrastructure that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks for file sharing that consists of millions of private, public, academic, business, and government packet switched networks, linked by a broad array of electronic, wireless, and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents and applications of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks for file sharing and telephony.
The origins of the Internet date back to research commissioned by the United States government in the 1960s to build robust, fault-tolerant communication via computer networks. While this work, together with work in the United Kingdom and France, led to important precursor networks, they were not the Internet. There is no consensus on the exact date when the modern Internet came into being, but sometime in the early to mid-1980s is considered reasonable.
From that point, the network experienced decades of sustained exponential growth as generations of institutional, personal From that point, the network experienced decades of sustained exponential growth as generations of institutional, personal, and mobile computers were connected to it.

used to interconnect network devices on the Internet.
TCP/IP implements layers of protocol stacks, and each layer provides a well-defined network services to the upper layer protocol. TCP and IP are the two protocols used by TCP/IP, as well as the (higher) application, (lower) data link and (lower) physical layer protocols

of parity bits to check that datato check that data has been transmitted accurately. The parity bit is added to every data unit (typically seven or eight bits ) that are transmitted. The parity bit for each unit is set so that all bytes have either an odd number or an even number of set bits.
Assume, for example, that two devicesAssume, for example, that two devices are communicating with even parity(the most common form of parity checking). As the transmitting device sends data, it counts the number of set bits in each group of seven bits. If the number of set bits is even, it sets the parity bit to 0; if the number of set bits is odd, it sets the parity bit to 1. In this way, every byte has an even number of set bits. On the receiving side, the device checks each byte to make sure that it has an even number of set bits. If it finds an odd number of set bits, the receiver knows there was an error during transmission.
The sender and receiver must both agree to use parity checking and to agree on whether parity is to be odd or even. If the two sides are not configured with the same parity sense, communication will be impossible

codes are a family of linear error-correcting codes that generalize the Hamming(7,4)-code are a family of linear error-correcting codes that generalize the Hamming(7,4)-code invented by Richard Hamming in 1950. Hamming codes can detect up to two-bit errors or correct one-bit errors without detection of uncorrected errors. By contrast, the simple parity code. By contrast, the simple parity code cannot correct errors, and can detect only an odd number of bits in error. Hamming codes are perfect codes. By contrast, the simple parity code cannot correct errors, and can detect only an odd number of bits in error. Hamming codes are perfect codes, that is, they achieve the highest possible rate. By contrast, the simple parity code cannot correct errors, and can detect only an odd number of bits in error. Hamming codes are perfect codes, that is, they achieve the highest possible rate for codes with their block length. By contrast, the simple parity code cannot correct errors, and can detect only an odd number of bits in error. Hamming codes are perfect codes, that is, they achieve the highest possible rate for codes with their block length and minimum distance 3

data, they can only detect and correct errors when the error rate is low. This is the case in computer memory (ECC memory), where bit errors are extremely rare and Hamming codes are widely used. In this context, an extended Hamming code having one extra parity bit is often used. Extended Hamming codes achieve a Hamming distance of , which allows the decoder to distinguish between when at most one bit error occurred and when two bit errors occurred. In this sense, extended Hamming codes are single-error correcting and double-error detecting, abbreviated as SECDED.

and controls computer hardware so that application software can perform a task. Operating systems, such as Microsoft Windows, Mac OS X or Linux, are prominent examples of system software. System software contrasts with application software, which are programs that enable the end-user to perform specific, productive tasks, such as word processing or image manipulation. System software performs tasks like transferring data from memory to disk, or rendering text onto a display device. Specific kinds of system software include loading programs, operating systems, device drivers, programming tools, compilers, assemblers, linkers, and utility software. Software libraries that perform generic functions also tend to be regarded as system software, although the dividing line is fuzzy; while a C runtime library is generally agreed to be part of the system, an OpenGL or database library is less obviously so. If system software is stored on non-volatile memory such as integrated circuits, it is usually termed firmware while an application software is a subclass of computer software that employs the capabilities of a computer directly and thoroughly to a task that the user wishes to perform. This should be contrasted with system software which is involved in integrating a computer's various capabilities, but typically does not directly apply them in the performance of tasks that benefit the user.

media players. Multiple applications bundled together as a package are sometimes referred to as an application suite. Microsoft Office and OpenOffice.org, which bundle together a word processor, a spreadsheet, and several other discrete applications, are typical examples. The separate applications in a suite usually have a user interface that has some commonality making it easier for the user to learn and use each application. And often they may have some capability to interact with each other in ways beneficial to the user. For example, a spreadsheet might be able to be embedded in a word processor document even though it had been created in the separate spreadsheet application. User-written software tailors systems to meet the user's specific needs. User-written software include spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is.