Well when Radio Shack was a thing, I got some intercoms that plugged into the 110 v outlets. Would work in any outlet on that service. It worked great when I had to go to areas of the asphalt plant while my operator was in our control room . In a 300 foot long tunnel the walkie talkies didn't work so good, and they were the expensive non-CB variety from a local commercial radio service. plus we could talk #h!t about others on the property without them hearing it on the radios :lol: