A questioner said:

Found three of these wall outlets in our new house, not sure what they are. It is a 100 year old house if that helps at all. Curious what it is for.

More info:

It’s just an outlet, same height and width as all the other standard AC outlets in the house, but it’s round and has a knob in the center. The one pictured is slightly damaged, but I’m more interested in what it is supposed to be.

The house is close to 100 years old, built in 1929. I’ve asked multiple people with electrical experience who don’t have a clue what it is for. I have searched “circular outlet” on google, and it’s given me basically nothing of use.

I’m curious what it is meant to plug in, as well as if it can be converted to an AC outlet. Any information you have would be helpful, thank you for your time.

Some of the answers were:

1. My electrical contractor husband said it’s an old 110 twist lock outlet.
2. It’s not twist lock. It’s transitional between parallel prongs like we have now and tandem prongs like preceded it.
3. It looks like a 2 pole 120v outlet that has a crack running down the middle
4. These appear to be the same ones. Listed as 10 amp 250v
5. It is a 110 volt outlet designed to accommodate the original 1906 vintage Hubbell style plug where the blades were arranged in “tandem” (later called NEMA 2-15) and a slightly later design with two parallel blades (patented by Hubbell in 1913) (later designated NEMA 1-15) so two T shaped slots could handle either plug style.

   This is from the knob and tube wiring era and if those plugs are live then you have knob and tube wiring in the walls.

   My Grandmother’s farmhouse which originally had 25Hz power coming from Niagara Falls had a few of these outlets.

6. looks like a gaint housefly
7. Fly messed with wrong knob and tube
8. That is a power outlet that can accept either a plug with parallel blades or one with tandem blades. You may also find that the black part is an insert that unscrews to reveal something that resembles a light bulb socket.

   Our current style three-pronged plugs and polarized two-pronged plugs (ones that can only fit in one direction) were preceded by plugs that were two-pronged and could fit either way. Those were preceded by plugs that had two blades in tandem rather than parallel.

   This outlet is transitional between parallel and tandem.

   Tandem was preceded by screw-in sockets, which were problematic because of the twists they put in the cord and also not particularly safe.

9. With outlets that old, I suspect the house has really primitive service. We looked at a place that was very old and it had 30A service. Ouch. And most of that was external with wire molding. Plaster walls, no one wanted to rip into to run wires.
10. Looks like an old 120v 20a outlet. Hard to tell so don’t take my word for it. Get an electrician or use a high voltage multi meter
11. It looks like a radio outlet but I’m no expert. It looks like there’s a piece that can be turned to make it for radios or a regular 2 prong outlet.
12. Where did you find this 100 year old house? Sounds like it should be on an historic registry or something
13. The way these old outlets were grounded is a fire hazard nightmare. Get a pro to look at it before you try to switch the outlet to a modern one and plug any modern things into.
14. I lived in a old Victorian home when I was really young, we had outlets that looked similar. I don’t know if I’m getting things confused but one of the outlets was a vacuum system that ran throughout the house and emptied in the basement. Probably WAY off!! lol but that just reminded me of it.
15. There is no ground wire in that box to be sure. You can buy a new 2 prong or protect the circuit with a gfi breaker.

What do you think? Let us know in the comment!

Nestled within the walls of your new abode, amidst the creaks of aged floorboards and whispers of history, lie secrets waiting to be uncovered. Imagine the intrigue of stumbling upon not one, but three peculiar wall outlets, their purpose shrouded in mystery. Such is the enigma that confronts inhabitants of century-old homes, sparking curiosity and beckoning exploration.

In the tapestry of architectural evolution, homes that have weathered a century possess an undeniable allure, each crack and crevice echoing with tales of generations past. Yet, amidst the nostalgia and charm, anomalies occasionally surface, hinting at bygone utilities and erstwhile conveniences.

For the uninitiated, encountering these antiquated wall outlets might evoke bewilderment. What purpose could they serve in an era vastly distinct from our own? As we embark on a journey of discovery, it becomes evident that these artifacts of yesteryear carry with them a legacy of innovation and adaptation.

The first clue lies in understanding the context of early 20th-century living. At the turn of the century, electricity was a burgeoning novelty, gradually illuminating homes and revolutionizing daily life. However, the transition from gas lamps to electric lighting was not instantaneous, leading to a coexistence of both systems during a period of technological transition.

Enter the mysterious wall outlets—relics of a bygone era when electricity was a luxury, not yet fully integrated into domestic infrastructure. These outlets, distinguished by their unique design and functionality, served a specific purpose: powering early electric lamps and appliances.

Known colloquially as “Edison outlets” or “gas and electric outlets,” these peculiar contraptions catered to the diverse needs of homeowners, offering compatibility with both electric and gas-powered devices. Their dual functionality was emblematic of an era marked by experimentation and adaptation, where innovation intersected with tradition.

The distinctive appearance of these outlets often betrays their dual nature. Positioned alongside conventional electrical outlets, they feature a circular socket for gas lighting fixtures and a smaller, adjacent socket for electric plugs. This ingenious design allowed homeowners to seamlessly transition between gas and electric lighting, accommodating varying preferences and technological capabilities.

As we delve deeper into the annals of architectural history, it becomes clear that these relics are more than mere curiosities—they are tangible links to a bygone era, testaments to the ingenuity and adaptability of past generations. Each outlet tells a story, whispering of an age when electricity was a marvel and innovation knew no bounds.

For homeowners fortunate enough to inherit these vestiges of the past, a sense of reverence and appreciation often accompanies the discovery. They are reminders of the journey humanity has undertaken, from the flickering glow of gas lamps to the dazzling brilliance of modern lighting systems.

In the modern era, where technological advancement unfolds at a rapid pace, it is easy to overlook the humble beginnings that paved the way for our present comforts. Yet, within the walls of century-old homes, reminders abound, urging us to pause and reflect on the legacy of innovation that surrounds us.

So, the next time you encounter a mysterious wall outlet in your century-old abode, take a moment to appreciate the history it represents. Behind its weathered facade lies a story waiting to be told—a story of resilience, adaptation, and the timeless quest for illumination in both the literal and metaphorical sense.