Macomb exchange insulator U-57

Porcelain insulators are said to increase the insulating efficiency of a line to a considerable degree. It is said that porcelain insulators do not condense moisture from the air, so that there is comparatively little leakage between telephone circuits and also to the ground. The insulator shown in the illustration is manufactured by the Illinois Electric Porcelain Co. of Macomb, Ill., and is of a size such as is commonly used for telephone lines.