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Concept
Noise (video)
Summary
Noise, commonly known as static, white noise, static noise, or snow, in analog video and television, is a random dot pixel pattern of static displayed when no transmission signal is obtained by the antenna receiver of television sets and other display devices.
The random pixel pattern is superimposed on the picture or the television screen, being visible as a random flicker of "dots", "snow" or "fuzzy zig-zags" in some television sets, is the result of electronic noise and radiated electromagnetic noise accidentally picked up by the antenna like air or cable. This effect is most commonly seen with analog TV sets, blank VHS tapes, or other display devices.
There are many sources of electromagnetic noise which cause the characteristic display patterns of static. Atmospheric sources of noise are the most ubiquitous, and include electromagnetic signals prompted by cosmic microwave background radiation, or more localized radio wave noise from nearby electronic devices.
The display device itself is also a source of noise, due in part to thermal noise produced by the inner electronics. Most of this noise comes from the first transistor the antenna is attached to.
UK viewers used to see "snow" on black after sign-off, instead of "bugs" on white, a purely technical artifact due to old 405-line British senders using positive rather than the negative video modulation used in Canada, the US, and (currently) the UK as well. Since one impression of the "snow" is of fast-flickering black bugs on a white background, the phenomenon is often called myrornas krig in Swedish, myrekrig in Danish, hangyák háborúja in Hungarian, Ameisenkrieg in German, and semut bertengkar in Indonesian, which all translate to 'war of the ants'.
It is also known as ekran karıncalanması in Turkish, meaning 'ants on the screen', hangyafoci 'ant football' in Hungarian, and purici 'fleas' in Romanian. In French however, this phenomenon is mostly called neige 'snow', just like in Dutch, where it is called sneeuw. In Portugal, it's called formigueiro 'anthill'.
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Noise (electronics)
In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics and central to thermodynamics. Any conductor with electrical resistance will generate thermal noise inherently. The final elimination of thermal noise in electronics can only be achieved cryogenically, and even then quantum noise would remain inherent. Electronic noise is a common component of noise in signal processing.