NAB: National Association of Broadcasters. An association of television and radio professionals that works to further the goals of the professional broadcast industry. Holds a rather large convention yearly in Las Vegas.

Negative Effect: Special effect in which either blacks and whites are reversed or colors are inverted. For example, red becomes a blue-green, green becomes purple, etc.

NLM: Network Loadable Module.

Noise: A general term used in electronics to indicate any unwanted electrical signal, unrelated to the original signal. Video noise is generally manifested as snow, graininess, ghost images or picture static induced by external sources such as the national power-line grid, electric motors, fluorescent lamps, etc. In audio, noise is generally manifested as hiss and static.

Noise Gate: A device used to modify a signal's noise characteristics. In video, noise gates provide optimal automatic suppression of snow (signal noise level). In audio, a noise gate provides a setable signal level threshold below which all sound is removed.

Noise Reduction: An electronic process used to reduce noise levels in audio and video. In video, the most effective noise reduction is accomplished by digitizing the video signal and carrying out a computerized pixel by pixel analysis of the data. In audio, the most effective systems employ an encode/decode scheme, performed before and after recording, such as the Dolby audio noise reduction system. Noise reduction can be performed on an existing audio signal using systems such as DNR (dynamic noise reduction) but are less effective because they also affect the audio signal.

Nonlinearity: The amount by which a measured video signal output differs from a standard video signal output. The greater this deviation, the greater the video signal distortion and possibility of luminance and chrominance problems.

Non-Linear Editing: The process of editing using rapid retrieval (random access) computer controlled media such as hard disks, CD-ROMs and laser discs. Its main advantages are:

- Allows you to reorganize clips or make changes to sections without having to redo the entire production.
- Very fast random access to any point on the hard disk (typically 20-40 ms)

NTSC: National Television Systems Committee of Electronic Industries Association (EIA) that prepared the standard of specifications approved by the Federal Communications Commission in 1953 for commercial broadcasting. NTSC is the standard for the U.S., Canada, Japan, Central America, 1/2 of the Caribbean & 1/2 of South America. (See PAL and SECAM.)

NTSC Format: A color television format having 525 scan lines; a field frequency of 60 Hz; a broadcast bandwidth of 4 MHz; line frequency of 15.75 KHz; frame frequency of 1/30 of a second; and a color subcarrier frequency of 3.58 MHz.