I moved into a house built in the 1950s in the north eastern US and this outlet is on the back of the house but I can't find anything like it searching online. If anyone knows what it is I'd greatly appreciate the enlightenment!
Thats good question, I might have to go antiquing to find something to try it out with.... although i suppose I'd have to pay to activate the line so maybe not.
And yeah I ruled out power right away since theres no poka-yoke feature to prevent mixing up hot, neutral, and ground, but "four prong outlet" and reverse image searching weren't getting me there.
