I was in the shower a moment ago when an idea hit me. We’re all familiar with how thermostat wire works. Basically the thermostat shorts two terminals together in the furnace when it wants heating, cooling, or fan. This requires several wires for most systems, and can be a big hurdle for folks in older homes if they want to install a smart thermostat or central air as they often only have 2 or 3 wires. This can require running new wire, which I had to do in my own home and was a pain in the ass that required cutting into my drywall and such. But, what if you didn’t need more than 2 wires? Imagine a technology that worked kinda like powerline does, Ethernet over electrical lines. On one end you have your thermostat with two terminals. On the other end, in your furnace, you have a device that converts those 2 wires to 4 or 5. It would work by sending 24v all the time, that way you have your C wire. Then when the thermostat calls for heat, intelligence within the thermostat sends a small pulse over the wire. The device previously mentioned in the furnace interprets this pulse, knows what to do based on frequency, converts that to a 4 or 5 wire schema the furnace can understand, and completes the call for heating and cooling. Why does this not exist? It would be a slight modification to existing, cheap technology, and would make running new thermostat wire a thing of the past.