... And indeed, it is an old house. In many of these, there is a single black, and a single white wire in the wall - In many of these older houses, the ground is the metal box and the BX cable that connects. The wiring is an actual switch between the power (black wire) and the neutral (white wire), where the power goes from the wire through the switch, out the white wire to the light, and then back through the rest of the wiring. It really is a typical setup in pre-WWII homes, and many post WWII homes. And therein lies the problem. I get power to the switch (the lights go on and blink., the little circle on the switch illuminates, and I can hear the relay kicking on and off - but no power is getting through to my overhead light. I've tried it with both of the black wires from the HS200 to my live power line, then each black wire individually, with the same result. The app finds the device, and shows the on/off switch exists - I can even name it- but otherwise, nothing. Any suggestions?