Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Object Groupings and Systems (hierarchy name)
4. systems (equipment)
5. [systems by function]
6. communication systems (mechanical and electrical systems)

Anotations

Scope note:

Formats and systems endorsed by the NTSC, which sets the television and video standards for the United States. The standard television signal set by the NTSC is composite video, which is compiled of red, blue, and green signals. The NTSC standard TV image has 525 horizontal lines per frame. Alternate standards include HDTV (high-definition television), as well as Phase Alternate Line (PAL) or Sequential Couleur avec Memoire (SECAM) primarily adopted in other areas of the world.