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XPDR
In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight transponder is an automated transceiver in an aircraft that emits a coded identifying signal in response to an interrogating received signal. In a communications satellite, a satellite transponder receives signals over a range of uplink frequencies, usually from a satellite ground station; the transponder amplifies them, and re-transmits them on a different set of downlink frequencies to receivers on Earth, often without changing the content of the received signal or signals. Satellite/broadcast communications A communications satellite’s channels are called transponders because each is a separate transceiver or repeater. With digital video data compression and multiplexing, several video and audio channels may travel through a single tr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transponder (aeronautics)
A transponder (short for ''trans''mitter-res''ponder'' and sometimes abbreviated to XPDR, XPNDR, TPDR or TP) is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar. Collision avoidance systems have been developed to use transponder transmissions as a means of detecting aircraft at risk of colliding with each other. Air traffic control units use the term "squawk" when they are assigning an aircraft a transponder code, ''e.g.'', "Squawk 7421". Squawk thus can be said to mean "select transponder code" or "squawking ''xxxx''" to mean "I have selected transponder code ''xxxx''". The transponder receives interrogation from the Secondary Surveillance Radar on 1030 MHz and replies on 1090 MHz. Secondary surveillance radar Secondary surveillance radar (SSR) is referred to as "secondary", to distinguish it from the "primary radar" that works by p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
407 Transponder
4 (four) is a number, numeral and digit. It is the natural number following 3 and preceding 5. It is the smallest semiprime and composite number, and is considered unlucky in many East Asian cultures. In mathematics Four is the smallest composite number, its proper divisors being and . Four is the sum and product of two with itself: 2 + 2 = 4 = 2 x 2, the only number b such that a + a = b = a x a, which also makes four the smallest squared prime number p^. In Knuth's up-arrow notation, , and so forth, for any number of up arrows. By consequence, four is the only square one more than a prime number, specifically three. The sum of the first four prime numbers two + three + five + seven is the only sum of four consecutive prime numbers that yields an odd prime number, seventeen, which is the fourth super-prime. Four lies between the first proper pair of twin primes, three and five, which are the first two Fermat primes, like seventeen, which is the third. On the other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wideband
In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the channel. Some communication links have such a high data rate that they are forced to use a wide bandwidth; other links may have relatively low data rates, but deliberately use a wider bandwidth than "necessary" for that data rate in order to gain other advantages; see '' spread spectrum''. A wideband antenna is one with approximately or exactly the same operating characteristics over a very wide Passband. It is distinguished from broadband antennas, where the passband is large, but the antenna gain and/or radiation pattern need not stay the same over the passband. The term Wideband Audio or (also termed HD Voice or Wideband Voice) denotes a telephony using a wideband codec, which uses a greater frequency range of the audio spectrum than conventional voiceband telephone calls, resulting in a clearer sound. Wideband in this context is usually considered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Grid
For telecommunications, a frequency grid is a table of all the central frequencies (and corresponding wavelengths) of channels allowed in a communications system. The most common frequency grid used for fiber-optic communication is that used for channel spacing in Dense Wavelength Division Multiplexing (DWDM) at wavelengths around 1550 nm and defined by ITU-T The ITU Telecommunication Standardization Sector (ITU-T) is one of the three sectors (divisions or units) of the International Telecommunication Union (ITU). It is responsible for coordinating standards for telecommunications and Information Comm ... G.694.1.ITU-T G.694.1, "Spectral grids for WDM applications: DWDM frequency gridITU-T website/ref> The grid is defined relative to 193.1 THz and extends from 191.7 THz to 196.1 THz with 100 GHz spacing. While defined in frequency, the grid is often expressed in terms of wavelength, in which case it covers the wavelength range of 1528.77 nm to 15 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter '' lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Full-duplex
A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX). In a full-duplex system, both parties can communicate with each other simultaneously. An example of a full-duplex device is plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party. There is a two-way communication channel between them, or more strictly speaking, there are two communication chann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Fiber
An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass ( silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data transfer rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer. Fibers are also used for illumination and imaging, and are often wrapped in bundles so they may be used to carry light into, or images out of confined spaces, as in the case of a fiberscope. Specially designed fibers are also used for a variety of other applications, some of them being fiber optic sensors and fiber laser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Fiber Communications
Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of infrared light through an optical fiber. The light is a form of carrier wave that is modulated to carry information. Fiber is preferred over electrical cabling when high bandwidth, long distance, or immunity to electromagnetic interference is required. This type of communication can transmit voice, video, and telemetry through local area networks or across long distances. Optical fiber is used by many telecommunications companies to transmit telephone signals, internet communication, and cable television signals. Researchers at Bell Labs have reached a record bandwidth–distance product of over kilometers per second using fiber-optic communication. Background 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 electric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Station (communications)
A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves from astronomical radio sources. Ground stations may be located either on the surface of the Earth, or in its atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency (SHF) or extremely high frequency (EHF) bands (e.g. microwaves). When a ground station successfully transmits radio waves to a spacecraft (or vice versa), it establishes a telecommunications link. A principal telecommunications device of the ground station is the parabolic antenna. Ground stations may have either a fixed or itinerant position. Article 1 § III of the International Telecommunication Union (ITU) Radio Regulations describes various types of stationary and mobile ground stations, and their interre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landline
A landline (land line, land-line, main line, home phone, fixed-line, and wireline) is a telephone connection that uses metal wires or optical fiber telephone line for transmission, as distinguished from a mobile cellular network, which uses radio waves for signal transmission. Characteristics A corded landline telephone made by Siemens from c. 1997 Landline service is typically provided through the outside plant of a telephone company's central office, or wire center. The outside plant comprises tiers of cabling between distribution points in the exchange area, so that a single pair of copper wire, or an optical fiber, reaches each subscriber location, such as a home or office, at the network interface. Customer premises wiring extends from the network interface to the location of one or more telephones inside the premises. The telephone connected to a landline can be hard-wired or cordless and typically refers to the operation of wireless devices or systems in fixed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single Channel Per Carrier
Single channel per carrier (SCPC) refers to using a single signal at a given frequency and bandwidth. Most often, this is used on broadcast satellites to indicate that radio stations are not multiplexed as subcarriers onto a single video carrier, but instead independently share a transponder. It may also be used on other communications satellites, or occasionally on non-satellite transmissions. In an SCPC system, satellite bandwidth is dedicated to a single source. This makes sense if it is being used for something like satellite radio, which broadcasts continuously. Another very common application is voice, where a small amount of fixed bandwidth is required. However, it does not make sense for burst transmissions like satellite internet access or telemetry, since a customer would have to pay for the satellite bandwidth even when they were not using it. Where multiple access is concerned, SCPC is essentially FDMA. Some applications use SCPC instead of TDMA, because they requ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Station
Radio broadcasting is transmission of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio station, while in satellite radio the radio waves are broadcast by a satellite in Earth orbit. To receive the content the listener must have a broadcast radio receiver (''radio''). Stations are often affiliated with a radio network which provides content in a common radio format, either in broadcast syndication or simulcast or both. Radio stations broadcast with several different types of modulation: AM radio stations transmit in AM ( amplitude modulation), FM radio stations transmit in FM ( frequency modulation), which are older analog audio standards, while newer digital radio stations transmit in several digital audio standards: DAB ( digital audio broadcasting), HD radio, DRM ( Digital Radio Mondiale). Television br ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
