ELECTRICAL ENCYCLOPEDIA

What is Wi-Fi?   Wi-Fi ( /ˈwaɪfaɪ/) or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, tablet, or digital audio player, can connect to the Internet via a wireless network access point. An access point (or hotspot) has a range of about 20 meters (65 ft) indoors and a greater range outdoors. Multiple overlapping access points can cover large areas. continue.. Brief History of Wi-Fi   In the beginning-Wi-Fi would certainly not exist without a decision taken in 1985 by the Federal Communications Commission (FCC), America's telecoms regulator, to open several bands of wireless spectrum, allowing them to be used without the need for a government licence. This was an unheard-of move at the time; other than the hamradio channels, there was very little unlicensed spectrum. But the FCC, prompted by a visionary engineer on its staff, Michael Marcus, took three chunks of spectrum fr

What is Bluetooth?   Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (using short wavelength radio transmissions in the ISM band from 2400-2480 MHz) from fixed and mobile devices, creating personal area networks (PANs) with high levels of security. Created by telecoms vendor Ericsson in 1994,[1] it was originally conceived as a wireless alternative to RS-232 data cables. It can connect several devices, overcoming problems of synchronization.  continue.. Brief History of Bluetooth   Bluetooth is a wireless technology that is built into electronic gadgets. It lets you talk and share information like music, voice, and videos wirelessly. Bluetooth technology uses radio waves just like mobile phones, television, and FM radio. The difference between those devices and Bluetooth technology is distance. Radios and television broadcast too many people over many miles. Bluetooth technology just sends information to your personal space. Thi

What is an X-RAY?   X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz (3×1016 Hz to 3×1019 Hz) and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma rays. In many languages, X-radiation is called Röntgen radiation, after Wilhelm Conrad Röntgen, who is usually credited as its discoverer, and who had named it X-radiation to signify an unknown type of radiation. Correct spelling of X-ray(s) in the English language includes the variants x-ray(s) and X ray(s). XRAY is used as the phonetic pronunciation for the letter x. continue.. History of X-RAY   All light and radio waves belong to the electromagnetic spectrum, and are all considered different types of electromagnetic waves, including: microwaves and infrared bands whose waves are longer than those of visible light (betwe

What is Thermography?   Infrared thermography, thermal imaging, and thermal video are examples of infrared imaging science. Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum (roughly 9000–14,000 nanometers or 9–14 µm) and produce images of that radiation, called thermograms. Since infrared radiation is emitted by all objects above absolute zero according to the black body radiation law, thermography makes it possible to see one's environment with or without visible illumination. The amount of radiation emitted by an object increases with temperature; therefore, thermography allows one to see variations in temperature. When viewed through a thermal imaging camera, warm objects stand out well against cooler backgrounds; humans and other warm-blooded animals become easily visible against the environment, day or night. As a result, thermography is particularly useful to military and other users of surveillance cameras.. continue.. An Over

What is INFRARED?   Infrared (IR) light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres (µm), and extending conventionally to 300 µm. These wavelengths correspond to a frequency range of approximately 1 to 400 THz,[1] and include most of the thermal radiation emitted by objects near room temperature. Microscopically, IR light is typically emitted or absorbed by molecules when they change their rotational-vibrational movements.  continue.. What is INFRARED Radiation?   The light we see with our eyes is really a very small portion of what is called the "Electromagnetic Spectrum." The Electromagnetic Spectrum includes all types of radiation - from the X-rays used at hospitals, to radio waves used for communication, and even the microwaves you cook food with. Radiation in the Electromagnetic Spectrum is often categorized by wavelength. Short wavelength radiation is of t

What is a touch screen technology?   A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. The term generally refers to touching the display of the device with a finger or hand. Touchscreens can also sense other passive objects, such as a stylus. Touchscreens are common in devices such as all-in-one computers, tablet computers, and smartphones. The touchscreen has two main attributes. First, it enables one to interact directly with what is displayed, rather than indirectly with a pointer controlled by a mouse or touchpad. Secondly, it lets one do so without requiring any intermediate device that would need to be held in the hand (other than a stylus, which is optional for most modern touchscreens). Such displays can be attached to computers, or to networks as terminals. They also play a prominent role in the design of digital appliances such as the personal digital assistant (PDA), satellite navigation devices, mob

What is a metal detector?   A metal detector is a device which responds to metal that may not be readily apparent. The simplest form of a metal detector consists of an oscillator producing an alternating current that passes through a coil producing an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, eddy currents will be induced in the metal, and this produces an alternating magnetic field of its own. If another coil is used to measure the magnetic field (acting as a magnetometer), the change in the magnetic field due to the metallic object can be detected.  continue.. How does a metal detector works?   Mention the words metal detector and you'll get completely different reactions from different people. For instance, some people think of combing a beach in search of coins or buried treasure. Other people think of airport security, or the handheld scanners at a concert or sporting event. continue.. History of Metal Detectors   In the

What is a SCADA?   The term SCADA usually refers to centralized systems which monitor and control entire sites, or complexes of systems spread out over large areas (anything from an industrial plant to a nation). Most control actions are performed automatically by RTUs or by PLCs. Host control functions are usually restricted to basic overriding or supervisory level intervention. For example, a PLC may control the flow of cooling water through part of an industrial process, but the SCADA system may allow operators to change the set points for the flow, and enable alarm conditions, such as loss of flow and high temperature, to be displayed and recorded. The feedback control loop passes through the RTU or PLC, while the SCADA system monitors the overall performance of the loop.  continue.. History of SCADA   SCADA (supervisory control and data acquisition) has been around as long as there have been control systems. The first ‘SCADA’ systems utilized data acquisition by means of panel

What is a SONAR?   Sonar (originally an acronym for SOund Navigation And Ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect other vessels. Two types of technology share the name "sonar": passive sonar is essentially listening for the sound made by vessels; active sonar is emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of "targets" in the water. Acoustic location in air was used before the introduction of radar.  continue.. History of SONAR   Sonar is a system that uses transmitted and reflected underwater sound waves to detect and locate submerged objects or measure the distances underwater. It has been used for submarine and mine detection, depth detection, commercial fishing, diving safety and communication at sea. The Sonar device will send out a subsurface sound wave an

What is a RADAR?   Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio waves or microwaves which bounce off any object in their path. The object returns a tiny part of the wave's energy to a dish or antenna which is usually located at the same site as the transmitter.  continue.. History of RADAR   In 1934 a large-scale Air Defence exercise was held to test the defences of Great Britain and mock raids were carried out on London. Even though the routes and targets were known in advance, well over half the bombers reached their targets without opposition. Prime Minister Baldwin's statement "The bomber will always get through" seemed true. To give time for their guns to engage enemy aircraft as they came over, the Army was ex