LAMPS are held in holders designed either to be suspended on the end of flexible conductors or to be screwed to bho ceiling or a rigid fitting. A holder consists of a brass casing in two parts, held together by a screwed collar and an internal porcelain base. The base includes two projecting spring terminals, against which plates in the lamp press when the lamp is inserted.

It is got at by first removing a collar, called the shade ring, and the shade kept in place by the collar; and then unscrewing the second collar, which holds the barrel, to which the lamp is attached by a bayonet1 joint, to the other part of the casing.

The porcelain base has a groove in each side, with which projections in the casing engage, to prevent the parts rotating relatively to each other when the collars are screwed up. When a lampholdcr is assembled, care must be taken to get these projections into the grooves, as otherwise the lamp will refuse to light up, because the holder terminals will then be out of lino with the lamp terminals and will not make contact. Some holders give trouble, because the projections are too small to get a proper grip on the porcelain, and the screwing up of collars causes a twist.

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