Special Features:

Nvis lamp socket shall have a detent to mechanically retain the lamp cap subassembly. The index on the lamp socket shall match the index on the cap, preventing the cap from being installed on the lamp socket in more than one direction. The index shall be oriented so that the center of the cap illumination in 180 degrees opposite of the index.

Properties:

An electric fitting primarily designed to electrically and mechanically accommodate a lamp. It may include an integral switch, transformer, or dropping resistor, provided these items control the lamp only. It does not include a shade, lens, reflector, or other item for modifying illumination. For items designed to mount on a conduit outlet, or junction box; see fixture, lighting.