Electrical Supply Company introduces new porcelain knob

New Porcelain Insulator.

The porcelain insulator shown in the cut is intended for out of door use, or for interior wiring where there is liability to dampness. Grooving of the outer surface, no doubt, adds somewhat to its insulating properties, but the chief advantage claimed consists in the setting of the screw head deep in the insulator; the main cause of leakage, that is a moisture circuit

New Porcelain Insulator.

from wire to screw, is thus avoided. It is one of several improved insulating devices lately introduced by the Electrical Supply company, Chicago.