National Association of Broadcasters. An American association which assists broadcasters in several ways including publishing technical information and sponsoring a number of trade shows and a large exhibition every year.

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A type of mix where the output at any point in the picture consists exclusively of whichever input signal had the greater amplitude. This is in contrast to a normal Mix which produces a linear sum of the inputs.

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A digital video effect that inverts the image RGB levels (effectively by subtracting them from Reference White level) so that it appears as photographic film negative. This effect may could be combined with complete de-saturation of the image.

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1. Any unwanted signal, usually not linked with TV picture content, for instance, interference from adjacent channel.

2. In general: a random signal as opposed to a regular signal, e.g. mains hum usually is not normally considered to be 'noise'.

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Test signal in a form of series of low level single channel bowties, with different frequencies to check the amplitude and frequency response of Coring devices. This should not to be confused with the 'bowtie' timing test signal.

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A device for improving signal to noise ratio by sophisticated filtering. Such devices can usually perform some other functions, e.g. synchronization or transcoding.

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Distance between viewer and TV picture at which the TV raster line structure becomes invisible. E. g. for 625 line system the recommended viewing distance is from 5 to 7 times screen height.

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Level of video signal corresponding to the white areas of a TV picture with nominal brightness. It depends on the Color TV System. This level usually serves as a 100 % reference level to calibrate the gains and settings of measurement devices.

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A type of mix where the output at any point in the picture consists exclusively of whichever input signal had the greater amplitude. This is in contrast to a normal mix which produces a linear sum of the inputs.

Synonyms: NAM

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Scanning with Interlace Ratio equal to unity.

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Non Return to Zero. A coding scheme that is polarity sensitive, usually a low signal level means logical '0' and high level means logical '1'. This coding scheme suffers the disadvantage that it contains frequency components from DC and is thus unsuitable.

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Non Return to Zero Inverse. A scrambling scheme that is polarity insensitive, usually low signal level means no change in logical values and high level means transition from one logical value to another, e. g. from '0' to '1' or from '1' to '0'.

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Vertical Interval Test Signal specified by NTC (a US body) for the NTSC system. It combines the features of VITS test lines CCIR-18 and CCIR-331.

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Vertical Interval Test Signal specified by NTC (a US body) for the NTSC system. Similar to VITS test line CCIR-330.

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Vertical Interval Test Signal specified by NTC (a US body) for the NTSC system. It combines the features of VITS test lines CCIR-18 and CCIR-331.

Synonyms: NTC Combination

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Vertical Interval Test Signal specified by NTC (a US body) for the NTSC system. Similar to VITS test line CCIR-330.

Synonyms: NTC Composite

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• TV system in which the chrominance signal is produced by Quadrature Balanced Modulation of color subcarrier. The modulating signals are the color difference signals I and Q. Note that the I and Q axes are rotated by 33 degrees with reference to the color burst subcarrier
• Acronym for National Television System Committee (USA), which first devised the system in 1953.

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Non-broadcast color TV system primarily used when certain modified PAL equipment is used for playing back consumer NTSC tapes with the color-under subcarrier heterodyning to 4.43 MHz instead of 3.58 MHz.

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Terms used in connection with sampling. Named after Harry Nyquist (Don't forget however the names of Whittaker, Kotelnikov and many others). The Nyquist rate is considered the minimum sampling frequency for correct digital reproduction of a given signal.

Synonyms: Nyquist Limit; Nyquist Rate

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See Nyquist Frequency.

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See Nyquist Frequency.

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