Item 74826 - Rubber pin-type insulator, ca. 1930 Item 74826 - Rubber pin-type insulator, ca. 1930 Contributed by Maine Historical Society Item 74826 Zoom 3296px x 4200px - 11.0"w x 14.0"h @ 300dpi | Need a larger size? *Credit line must read: Collections of Maine Historical Society Image Info Rubber insulators were a common replacement for glass pin-type insulators on telephone lines between 1930 and 1980. In some areas, the glass insulators had proved tempting targets for thrown rocks or gunfire. Insulators are needed on electric lines to prevent the electricity from "leaking" out of the wire. Show Details