Abbreviation for network terminal number.

1. Network Termination Point
2. Network Time Protocol

National Television Systems Committee

Abbreviation for National Television Standards Committee standard. The North American standard (525-line interlaced raster-scanned video) for the generation, transmission, and reception of television signals.
Note 1: In the NTSC standard, picture information is transmitted in vestigial-sideband AM and sound information is transmitted in FM.
Note 2: In addition to North America, the NTSC standard is used in Central America, a… (Read More →)

1. An expression of the extent to which the performance of a system, facility, or device is expected to degrade in a given nuclear environment.
2. The physical attributes of a system or component that will allow survival in an environment that includes nuclear radiation and electromagnetic impulses (EMI).
Note 1: Nuclear hardness may be expressed in terms of either… (Read More →)

In an antenna radiation pattern, a zone in which the effective radiated power is at a minimum relative to the maximum effective radiated power of the main beam.
Note 1: A null often has a narrow directivity angle compared to that of the main beam. Thus, the null is useful for several purposes, such as radio navigation and suppression of… (Read More →)

In transmission systems, a control character (a) that is used to accomplish media-fill stuffing or a time-fill stuffing in storage device or in a data transmission line and (b) that may be inserted and removed from a series of characters without affecting the meaning of the series.
Note: The null character may affect the control of equipment or the format… (Read More →)

The Number Portability Administration Centers (NPACs) are the registries that enable consumers and businesses in the U. S. and Canada to maintain their telephone numbers when they change service providers. The US NPAC contains routing information on ported TNs and pooled blocks and facilitates the updating of the routing databases of all subtending SPs in the portability area. The Canadian… (Read More →)

1. A defined geographic area identified by a unique three-digit code used in the North American Number Plan Area. [T1.207-1998] [T1.209-1998]
Note 1: Defined geographic area could mean the entire area encompassed by the North American Numbering Plan Area (for 800, 888, 877 codes, etc. ).
Note 2: By virtue of the overlay concept deployed in some states, there may… (Read More →)

1. The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element, multiplied by the refractive index of the medium in which the vertex of the cone is located.
Note: The NA is generally measured with respect to an object or image point and will vary as that… (Read More →)