what is lcd and led ?

"LED TV" redirects here. For true LED displays, see LED display. For true Liquid-crystal display, see Liquid-crystal display.

 

   An Apple iPod Touch disassembled to show   the array of white-edge LEDs powered on with the device

A LED-backlit LCD is a flat panel display which uses LED backlighting instead of the cold cathode fluorescent (CCFL) backlighting.LED-backlit displays use the same TFT LCD (thin-film-transistor liquid-crystal display) technologies as CCFL-backlit displays, but offer reduced energy consumption, better contrast and brightness, greater color range (using more expensive RGB LEDs, blue LEDs with RG phosphors, or quantum dot enhancement film (QDEF)), more rapid response to changes in scene (with dynamic backlight dimming), and photorefractive effects.
While not an LED display, a television using such a combination of an LED backlight with an LCD panel is called an LED TV by some manufacturers and suppliers

 Advantages
 Offer a wider color gamut (with RGB-LED or QDEF)
Allow a wider dimming range
Can be extremely slim (some screens are less than 0.5 inch, or 1.27 cm) thin in edge-lit panels
Are significantly lighter, often as much as half the total chassis and system weight of a comparable CCFL
Run significantly cooler
Have (typically) 20–30% lower power consumption (and longer lifespans)
Are more reliable
Produce less environmental pollution on disposal

 LED Arrangement
 LED backlights replace CCFL (fluorescent) lamps with several dozen to several hundred white or blue LEDs. Two types of LED arrangement may be used:

Edge-lit LEDs

LEDs form a line around the rim of the screen, with a special diffusion panel (light guide) to spread the light evenly behind the screen

Direct LED full array

LEDs form an array directly behind the screen at equally spaced intervals

In Full array local dimming (FALD), LEDs are controlled individually to dynamically control the level of light intensity in a given part of the screen. This method of backlighting allows local dimming of specific areas of darkness on the screen, resulting in much higher dynamic-contrast ratios, though at the cost of less detail in small, bright objects on a dark background, such as star fields or shadow details

 Technology
 LED-backlit LCDs are not self-illuminating (unlike pure-LED systems). There are several methods of backlighting an LCD panel using LEDs, including the use of either white or RGB (Red, Green, and Blue) LED arrays behind the panel and edge-LED lighting (which uses white LEDs around the inside frame of the TV and a light-diffusion panel to spread the light evenly behind the LCD panel). Variations in LED backlighting offer different benefits. The first commercial full-array LED-backlit LCD TV was the Sony Qualia 005 (introduced in 2004), which used RGB LED arrays to produce a color gamut about twice that of a conventional CCFL LCD television. This was possible because red, green and blue LEDs have sharp spectral peaks which (combined with the LCD panel filters) result in significantly less bleed-through to adjacent color channels. Unwanted bleed-through channels do not "whiten" the desired color as much, resulting in a larger gamut. RGB LED technology continues to be used on Sony BRAVIA LCD models. LED backlighting using white LEDs produces a broader spectrum source feeding the individual LCD panel filters (similar to CCFL sources), resulting in a more limited display gamut than RGB LEDs at lower cost.
The commercially called "LED TV's" are LCDs-based television sets where the LED's are dynamically controlled using the video information (dynamic backlight control or dynamic “local dimming” LED backlight, also marketed as HDR, high dynamic range television, invented by Philips researchers Douglas Stanton, Martinus Stroomer and Adrianus de Vaan ).
The evolution of energy standards and the increasing public expectations regarding power consumption have made it necessary for backlight systems to manage their power. As for other consumer electronics products (e.g., fridges or light bulbs), energy consumption categories are enforced for television sets. Standards for power ratings for TV sets have been introduced, e.g., in the USA, EU, and Australia as well as in China Moreover, a 2008 study showed that among European countries, power consumption is one of the most important criteria for consumers when they choose a television, as important as the screen size
Using PWM (pulse-width modulation, a technology where the intensity of the LEDs are kept constant but the brightness adjustment is achieved by varying a time interval of flashing these constant light intensity light sources, the backlight is dimmed to the brightest color that appears on the screen while simultaneously boosting the LCD contrast to the maximum achievable levels, drastically increasing the perceived contrast ratio, increasing the dynamic range, improving the viewing angle dependency of the LCD and drastically reducing the power consumption.

Fiber-optic communication

     Fiber optic communication

Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information.Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference are required.

Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication, and cable television signals. Researchers at Bell Labs have reached internet speeds of over 100 petabit×kilometer per second using fiber-optic communication.

First developed in the 1970s, fiber-optics have revolutionized the telecommunications  industry and have played a major role in the advent of the Information Age. Because of its advantages over electrical transmission, optical fibers have largely replaced copper wire communications in core networks in the developed world.

*The process of communicating using fiber-optics involves the following basic steps:

*creating the optical signal involving

*the use of a transmitter, usually from an electrical signal

*relaying the signal along the fiber, ensuring that the signal does not

*become too distorted or weak
receiving the optical signal

*converting it into an electrical signal

                 
Optical fiber is used by many telecommunications companies to transmit telephone signals, Internet communication and cable television signals. Due to much lower attenuation and interference, optical fiber has large advantages over existing copper wire in long-distance, high-demand applications. However, infrastructure development within cities was relatively difficult and time-consuming, and fiber-optic systems were complex and expensive to install and operate. Due to these difficulties, fiber-optic communication systems have primarily been installed in long-distance applications, where they can be used to their full transmission capacity, offsetting the increased cost. The prices of fiber-optic communications have dropped considerably since 2000.

The price for rolling out fiber to the home has currently become more cost-effective than that of rolling out a copper based network. Prices have dropped to $850 per subscriber[citation needed] in the US and lower in countries like The Netherlands, where digging costs are low and housing density is high.

                  Thecnology

Modern fiber-optic communication systems generally include an optical transmitter to convert an electrical signal into an optical signal to send through the optical fiber, a cable containing bundles of multiple optical fibers that is routed through underground conduits and buildings, multiple kinds of amplifiers, and an optical receiver to recover the signal as an electrical signal. The information transmitted is typically digital information generated by computers, telephone systems and cable television  companies.

The most commonly used optical transmitters are semiconductor devices such as light-emitting diodes (LEDs) and laser diodes. The difference between LEDs and laser diodes is that LEDs produce incoherent light, while laser diodes produce coherent light. For use in optical communications, semiconductor optical transmitters must be designed to be compact, efficient and reliable, while operating in an optimal wavelength range and directly modulated at high frequencies.

In its simplest form, an LED is a forward-biased p-n junction, emitting light through spontaneous emission, a phenomenon referred to as electroluminescence. The emitted light is incoherent with a relatively wide spectral width of 30–60 nm. LED light transmission is also inefficient, with only about 1%[citation needed] of input power, or about 100 microwatts, eventually converted into launched power which has been coupled into the optical fiber. However, due to their relatively simple design, LEDs are very useful for low-cost applications.

Communications LEDs are most commonly made from Indium gallium arsenide phosphide (InGaAsP) or gallium arsenide  (GaAs). Because InGaAsP LEDs operate at a longer wavelength than GaAs LEDs (1.3 micrometers vs. 0.81–0.87 micrometers), their output spectrum, while equivalent in energy is wider in wavelength terms by a factor of about 1.7. The large spectrum width of LEDs is subject to higher fiber dispersion, considerably limiting their bit rate-distance product (a common measure of usefulness). LEDs are suitable primarily for local-area-network applications with bit rates of 10–100 Mbit/s and transmission distances of a few kilometers. LEDs have also been developed that use several quantum wells to emit light at different wavelengths over a broad spectrum and are currently in use for local-area WDM  (Wavelength-Division Multiplexing) networks.

How do work mobile phone

        Mobile phone how work

In the most basic form, a mobile phone is essentially a two-way radio, consisting of a radio transmitter and a radio receiver. When you chat with your friend on your mobile phone, your phone converts your voice into an electrical signal, which is then transmitted via radio waves to the nearest cell tower. The network of cell towers then relays the radio wave to your friend’s mobile phone, which converts it to an electrical signal and then back to sound again. In the basic form, a mobile phone works just like a walkie-talkie.

 In additional to the basic function of voice calls, most modern mobile phone come with additional functions such as web surfing, taking pictures, playing games, sending text messages and playing music. More sophisticated smart phones can perform similar functions of a portable computer.

                  Radio frequency

Mobile phone use radio waves to communicate. Radio waves transport digitized voice or data in the form of oscillating electric and magnetic fields, called the electromagnetic field (EMF). The rate of oscillation is called frequency. Radio waves carry the information and travel in air at the speed of light.

Digital Revolution

                  Digital Revolution

           In the second half of the 20th Century, life was transformed around the world as digital technology rapidly advanced and became more accessible.

     The Digital Revolution Defined

              The Digital Revolution began between the late 1950’s and 1970’s. It is the development of technology from mechanical and analog to digital.
            During this time, digital computers and digital record keeping became the norm.
           The introduction of digital technology also changed the way humans communicate, now via computers, cell phones, and the internet.
         This revolution led way to the Information Age.
Historical Development of Digital Technology

            The 1947 invention of the               revolutionary transistor is     credited with sowing the seed for digital technology to come.
          By the 1950’s and 1960’s, many            governments, military forces, and other organizations were already using computers. Soon after, the computer was introduced for household use and by the 1970’s, many families had computers for personal use.

             This occurred at around the same time that video games became popular, both for home systems and arcade use. The infiltration of digital technology even led to the creation of jobs.
            As businesses moved to digital records keeping, the need for data entry clerks grew. The 1980’s brought computer production to films, robots to industry, and automated teller machines (ATMs) to banks. By 1989, 15% of all households in the US owned a computer.
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             Analog mobile phones made way to digital mobile phones in 1991 and the demand soared. This was the same year that the internet was made available to the public.
               By the end of the decade, the internet was so popular that many businesses had a website and nearly every country on earth had a connection. 
                When the 21st century began, cell phones were a common possession and high-definition television became the most common broadcasting method, replacing analog television.
                 By 2015, around 50% of the world had constant internet connection, and ownership rates of smartphones and commonness of tablet possession have nearly surpassed those of home computers.                     The ability to store information has grown exponentially with terabyte storage now being very accessible

The Digital Revolution Defined

The Digital Revolution began between the late 1950’s and 1970’s. It is the development of technology from mechanical and analog to digital. During this time, digital computers and digital record keeping became the norm. The introduction of digital technology also changed the way humans communicate, now via computers, cell phones, and the internet. This revolution led way to the Information Age.
Historical Development of Digital Technology

The 1947 invention of the revolutionary transistor is credited with sowing the seed for digital technology to come.
           By the 1950’s and 1960’s, many governments, military forces, and other organizations were already using computers. Soon after, the computer was introduced for household use and by the 1970’s, many families had computers for personal use. This occurred at around the same time that video games became popular, both for home systems and arcade use.
          The infiltration of digital technology even led to the creation of jobs. As businesses moved to digital records keeping, the need for data entry clerks grew.
          The 1980’s brought computer production to films, robots to industry, and automated teller machines (ATMs) to banks. By 1989, 15% of all households in the US owned a computer. Analog mobile phones made way to digital mobile phones in 1991 and the demand soared.

           This was the same year that the internet was made available to the public. By the end of the decade, the internet was so popular that many businesses had a website and nearly every country on earth had a connection.
            When the 21st century began, cell phones were a common possession and high-definition television became the most common broadcasting method, replacing analog television.

           By 2015, around 50% of the world had constant internet connection, and ownership rates of smartphones and commonness of tablet possession have nearly surpassed those of home computers.
        The ability to store information has grown exponentially with terabyte storage now being very accessible

Electronic waste

                  Electronic waste or e-waste describes discarded electrical or electronic devices. Used electronics which are destined for reuse, resale, salvage, recycling, or disposal are also considered e-waste.                                                       Informal processing of e-waste in developing countries can lead to adverse human health effects and environmental pollution.
The processes of dismantling and disposing of electronic waste in developing countries led to a number of environmental impacts as illustrated in the graphic. Liquid and atmospheric releases end up in bodies of water, groundwater, soil, and air and therefore in land and sea animals – both domesticated and wild, in crops eaten by both animals and human, and in drinking water.[52]

One study of environmental effects in Guiyu, China found the following:[53]

Airborne dioxins – one type found at 100 times levels previously measured
Levels of carcinogens in duck ponds and rice paddies exceeded international standards for agricultural areas and cadmium, copper, nickel, and lead levels in rice paddies were above international standards
Heavy metals found in road dust – lead over 300 times that of a control village's road dust and copper over 100 timescomponents, such as CPUs, contain potentially harmful components such as lead, cadmium, beryllium, or brominated flame retardants. Recycling and disposal of e-waste may involve significant risk to health of workers and communities in developed countries.
and great care must be taken to avoid unsafe exposure in recycling operations and leaking of materials such as heavy metals from landfills and incinerator ashes.

Rapid changes in technology, changes in media (tapes, software, MP3), falling prices, and planned obsolescence have resulted in a fast-growing surplus of electronic waste around the globe. Technical solutions are available, but in most cases, a legal framework, a collection, logistics, and other services need to be implemented before a technical solution can be applied.

Display units (CRT, LCD, LED monitors), processors (CPU, GPU, or APU chips), memory (DRAM or SRAM), and audio components have different useful lives. Processors are most frequently out-dated (by software no longer being optimized) and are more likely to become "e-waste" while display units are most often replaced while working without repair attempts, due to changes in wealthy nation appetites for new display technology. This problem could potentially be solved with modular smartphones or Phonebloks. These types of phones are more durable and have the technology to change certain parts of the phone making them more environmentally friendly. Being able to simply replace the part of the phone that is broken will reduce e-waste. An estimated 50 million tons of E-waste are produced each year.The USA discards 30 million computers each year and 100 million phones are disposed of in Europe each year. The Environmental Protection Agency estimates that only 15–20% of e-waste is recycled, the rest of these electronics go directly into landfills and incinerators.

In 2006, the United Nations estimated the amount of worldwide electronic waste discarded each year to be 50 million metric tons.According to a report by UNEP titled, "Recycling – from E-Waste to Resources," the amount of e-waste being produced – including mobile phones and computers – could rise by as much as 500 percent over the next decade in some countries, such as India.The United States is the world leader in producing electronic waste, tossing away about 3 million tons each year. China already produces about 2.3 million tons (2010 estimate) domestically, second only to the United States. And, despite having banned e-waste imports, China remains a major e-waste dumping ground for developed countries.

The processes of dismantling and disposing of electronic waste in developing countries led to a number of environmental impacts as illustrated in the graphic. Liquid and atmospheric releases end up in bodies of water, groundwater, soil, and air and therefore in land and sea animals – both domesticated and wild, in crops eaten by both animals and human, and in drinking water.

One study of environmental effects in Guiyu, China found the following:[53]

Airborne dioxins – one type found at 100 times levels previously measured
Levels of carcinogens in duck ponds and rice paddies exceeded international standards for agricultural areas and cadmium, copper, nickel, and lead levels in rice paddies were above international standards
Heavy metals found in road dust – lead over 300 times that of a control village's road dust and copper over 100 times

"Android" what is

                            Android

Android is a mobile operating system  developed by Google, based on a modified version of the Linux kernel and other open source software and designed primarily for touchscreen mobile devices such as smartphones and tablets. In addition, Google has further developed Android TV for televisions, Android Auto for cars, and Wear OS for wrist watches, each with a specialized user interface. Variants of Android are also used on game consoles, digital cameras, PCs  and other electronics.

*Initially developed by Android Inc., which Google bought in 2005, Android was unveiled in 2007, with the first commercial Android device launched in September 2008. The operating system has since gone through multiple major releases, with the current version being 8.1 "Oreo", released in December 2017. The core Android source code is known as Android Open Source Project (AOSP), and is primarily licensed under the Apache License.
Initially developed by Android Inc., which Google bought in 2005, Android was unveiled in 2007, with the first commercial Android device launched in September 2008. The operating system has since gone through multiple major releases, with the current version being 8.1 "Oreo", released in December 2017. The core Android source code is known as Android Open Source Project (AOSP), and is primarily licensed under the Apache License.

Android is also associated with a suite of proprietary software developed by Google, including core apps for services such as Gmail and Google Search, as well as the application store and digital distribution  platform Google Play, and associated development platform. These apps are licensed by manufacturers of Android devices certified under standards imposed by Google, but AOSP has been used as the basis of competing Android ecosystems, such as Amazon.com's Fire OS, which utilize their own equivalents to the Google Mobile Services.

What is mobile application.......?

               Mobile application

**A mobile application, most commonly referred to as an app, is a type of application software designed to run on a mobile device, such as a smartphone or tablet computer.

**Mobile applications frequently serve to provide users with similar services to those accessed on PCs. Apps are generally small, individual software units with limited function.

**This use of app software was originally popularized by Apple Inc. and its App Store, which offers thousands of applications for the iPhone, iPad and iPod Touch.

**A mobile application also may be known as an app, web app, online app, iPhone app or smartphone app.
Mobile applications are a move away from the integrated software systems generally found on PCs. Instead, each app provides limited and isolated functionality such as a game, calculator or mobile web browsing.

**Although applications may have avoided multitasking because of the limited hardware resources of the early mobile devices, their specificity is now part of their desirability because they allow consumers to hand-pick what their devices are able to do.

**The simplest mobile apps take PC-based applications and port them to a mobile device. As mobile apps become more robust, this technique is somewhat lacking.
**A more sophisticated approach involves developing specifically for the mobile environment, taking advantage of both its limitations and advantages. For example, apps that use location-based features are inherently built from the ground up with an eye to mobile given that the user does not have the same concept of location on a PC.

**A mobile app is a computer program  designed to run on a mobile device such as a phone/tablet or watch.

**Mobile applications often stand in contrast to desktop applications which run on desktop computers, and with web applications which run in mobile web browsers rather than directly on the mobile device.

**In 2009, technology columnist David Pogue  said that newer smartphones could be nicknamed "app phones" to distinguish them from earlier less-sophisticated smartphones.[1]The term "app", which is short for "software application", has since become very popular: In 2010, it was listed as "Word of the Year" by the American Dialect Societ

**Most mobile devices are sold with several apps bundled as pre-installed software, such as a web browser, email client, calendar, mapping program, and an app for buying music, other media, or more apps. Some pre-installed apps can be removed by an ordinary uninstall process, thus leaving more storage space for desired ones.

**Where the software does not allow this, some devices can be rooted to eliminate the undesired apps.

**Apps that are not preinstalled are usually available through distribution platforms called app stores. They began appearing in 2008 and are typically operated by the owner of the mobile operating system, such as the Apple App Store, Google Play, Windows Phone Store, and BlackBerry App World.

**However, there are independent app stores, such as Cydia, GetJar  and F-Droid. Some apps are free, while others must be bought. Usually, they are downloaded from the platform to a target device, but sometimes they can be downloaded to laptops or desktop computers. For apps with a price, generally a percentage, 20-30%, goes to the distribution provider (such as iTunes), and the rest goes to the producer of the app.
**The same app can, therefore, cost a different price depending on the mobile platform.

Apps can also be installed manually, for example by running an Android application package on Android devices.