This item has a rich history, dating back to the mid to late 1800s to the 1910s, when it was recognized as an Edison base receptacle.
During that era, people would screw in their fittings, attach the cord, and plug in various appliances, particularly those used in kitchens and bathrooms.
Originally, it had a cover. These receptacles predate the standard ones we use today, and they contribute to the origin of the term ‘wall socket.’ In the 1890s, homes typically had either knob and tube wiring or old BX wiring. For those with BX wiring, it’s advisable to inspect the outer covering to ensure it hasn’t rusted.
When these receptacles were installed, they likely operated on DC (direct current), especially if it was in a rural area where there might have been a 32-volt DC plant in the cellar or an outbuilding.
Source: fadnews24.com
