There are smart light switches in the market that are Wi-Fi controlled like Plumlife (formerly ube)
and Belkin WeMo. I wonder how they control the electricity that they operate on.
When I unplug my old fashioned light switch, I see that there are two wires. I believe that they work in this way.
But in smart switches, there must be some inner circuit that contains a relay inside of the smart light switch. If current goes through that circuit, that means smart light switch is closed too; therefore bulb is on all the time.
How do these products run on and control the same electric wire. If there is an external power source that feeds smart light switch like a fellow stackexchanger mentions in this question , I understand. But there is not. So what I ask is how is it possible to feed a circuit that controls it's own electricity.