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Glossary - N
- N/C & N/O alarms
N/C refers to normally closed, and N/O is Normally opened. It is used to describe alarm connections in security and CCTV.
National Bureau of Standards(USA).
- ND filters
Neutral Density filters are optical filters that attenuate the light a number of times. This attenuation is equal for all the wavelengths therefore it does not change the colour balance of an image, hence the term neutral.
A photometric unit for measuring luminace. One nit is equal to one candela per square metre of a projected surface area.
An unwanted signal produced by all electrical circuits working above the absolute zero. Noise can not be eliminated but only minimised.
National Television System Committee, an American committee which set the standards for colour television as used today in USA, Canada, Japan and a few other countries.