Lighting Terminology

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BASE - When used in reference to light bulbs (lamps), it is the portion of the lamp designed to fit into a lamp holder or socket.  (It is not a reference to any socket or lamp holder.  Bulbs (lamps) have a base; and fixtures have sockets.)

BI-PIN - having two pins, as in a "bi-pin base" of a certain kind of light bulb.

SOCKET - A device designed to hold a lamp (a light bulb) and to complete the power circuit to the lamp.  Other terms include lamp holder or lampholder, although the latter isn't a proper rendering.

SOCKET ADAPTER - A device designed to alter a socket.  By definition, then, this device is designed to fit a specific kind of socket and to alter it in a specific way.  Therefore the first descriptor for a socket adapter is in reference to the type of socket to be altered; and the second descriptor is in reference to the resulting alteration.  "Medium - to - Candelabra," for instance, is a socket adapter that will alter a medium socket so that it will accept candelabra light bulb bases.  "Candelabra - to - Medium," for instance, will alter a candelabra socket so that it will accept medium bulb bases.

OC - "On Center," also represented as O.C., o.c., the precise spacing of holes, pins, etc. expressed as the distance from the center of one hole/pin to the center of another.  Example:  two sample bi-pin sockets have identical OC dimensions, but one is designed for thicker pins, so the distance between the holes will be shorter, so measuring between the holes is close to useless.  Working with the bi-pin bulb, it's quite easy to determine the base of the bulb.


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