You could use UPB to signal over the home wiring to another device. https://en.wikipedia.org/wiki/Universal_powerline_bus https://en.wikipedia.org/wiki/Univers

You could use UPB to signal over the home wiring to another device. https://en.wikipedia.org/wiki/Universal_powerline_bus https://en.wikipedia.org/wiki/Universal_powerline_bus (Well, I guess there are several different protocols in this area, with their respective transceivers available. I used to use X-10, which has a much lower data rate.)