Insulators are non-electrical conducting objects, usually made of glass or porcelain, intended to insulate the current running in a wire from grounding out, especially in fog or rain. Most often they are mounted on wooden pins on the cross arms of telephone poles. In the 1840s, glass insulators emerged with the invention of the telegraph. These telegraph insulators were mostly threadless, pin-type insulators. The very first glass insulator was used by Samuel F. B. Morse on the line from Baltimore to Washington.

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拍攝者： Williamsphere