I recently had to replace a malfunctioning motion sensor on a driveway floodlight fixture. The new sensor stated that it required there to be a switch in the circuit. My question is why would there be any need for this? The light doesn't work automatically without power, so a switch seems pretty silly. I can't see where the sensor can tell whether there's a switch in the circuit or not, and technically, wouldn't the GFCI that powers it and the breaker in the service panel protecting it count as switches?
Now, a wall switch has been added to this circuit because there is relatively frequent occasion that the user needs to keep the floodlight from coming on. I'm just curious why the manufacturer would spec a switch.
Thoughts and opinions?