Fig. 270,b is installed in a single-gang box. The lamp extends through the plate and is protected by a perforated cage which extends about an inch from the plate.
Wall and Ceiling Sockets.
—One-light ceiling receptacles may be selected from the types shown in Figs. 272,a, b, c, d and e.
Fig. 272,a is of a type to fit standard 3¼-inch or 4-inch outlet boxes.
Fig. 272,b is of the small concealed-base type.
Fig. 272,c is of the large concealed-base type.
Fig. 272,d is of the insulated-base type.
Fig. 272,e is of the porcelain-base type.
Sockets in cellars shall be made entirely of porcelain. Those in bathrooms shall be entirely of porcelain and of the pull type.