Bit of a long-shot here, but has anyone played with the French heating control system called "fil pilote"? It's a single control wire interface to [multiple] heaters to enable you to remote control them.
An appartment has fil pilote heaters, but currently doesn't have any of the control wires connected, so the heaters are all just self controlled. Fortunately, there's a spare cable in all the conduit to the heaters, so connecting up the fil pilote wire will be very easy (looks like it was meant to be done originally).
Just thinking about remote interface to the system via phone.
The fil pilot protocol looks to have started simple and got more complex bits added over time, but I only need the simple bits. It's something like: Pilot wire disconnected or connected to neutral - heaters on. Pilot wire connected to live - heaters in setback mode. Pilot wire connected to live via diode - heaters off. Pilot wire connected to live via diode other way - something else which I can't remember. Various duration timed pulses can be used to change heater thermostat settings.
I'm probably only interested in being able to select on, setback mode, and possibly off. Just wondering if anyone else has played with this interface?