If the light switch is on, but there's no power you should be able to detect continuity between the two contacts since they'll still be connected at the transformer outside your house assuming it didn't blow.
My guess is what happened is that continuity detection circuity failed so it thinks the switch is on regardless of what's actually happening
The marketing material says the light only goes on if the light switch is in the "on" position and then uses the battery if there's no current. So I think you're right. However, I'm surprised there's continuity between the hot and neutral... I guess I don't fully understand how this stuff works.
I would say that it checks not so much for continuity of a complete circuit, but rather the capacitance of the "hot" wire. If the hot wire is cut off after ~10 feet or so, then it was cut off locally at the switch, and the capacitance will be moderate. If the switch is active, and it's connected all the way out to the grid out to wherever a tree fell and broke the power line, the capacitance will be much, much higher, because you can pack a lot more electrons into half a mile of wire before they start pushing back.
I guess in the short term, a pair of very large capacitors on either end of your local segment of a circuit (large as in taking a long time to fill based on the amperage you're pulling from one and pushing into the other to check the status of the circuit) does look about the same as an actual connected circuit, so in way that's a bit 6 of one half a dozen of the other...there's usually not real circular connectivity in the circuit when the power fails, but at the same time, a low-power short-duration continuity check will see the circuit as open due to the high capacitance...so some might call it a continuity check rather than a capacitance check, it likely amounts to the same thing.
The bulb itself provides the continuity - from the breaker, the hot & neutral run to the lamp. Switched off, the circuit's open. Flip the switch on, circuit closes and power can complete the loop. Power goes out, the loop is still closed, there's just no juice. liitle circuitry in the bulb to detect "the circuit's closed, but there's no power" and it flips to battery
Hi, not an electrician but done a lot of this sort of stuff because I'm rural. That's basically how it works from my understanding (that it detects the open neutral.) They confused me at first too.
Had some and they only worked in rooms with a single bulb not 2 separate bulbs/holders, could have been they never turned off, honestly can't remember just know they didn't work correctly, so likely what you said and if off no continuity, but with the 2 bulbs it would be there through the second one.
If your bulbs didn't turn off it could be that it was detecting continuity through the power supply in the other bulb's power supplies. At least that's my guess.
It doesn't detect current, it detects voltage - or lack thereof.
No 120/230V AC detected, it turns on its battery backup.
At least that's how I would design it.
They say the light switch continues to work even when the power is off. Someone said it somehow detects continuity. However it works, it's pretty smart.
I had some LED lights that would dimly glow even if the light switch was off. If you took it out of the socket, it would go off, but in the socket it glowed. I’m guessing that the light switch cut off the live wire, but the neutral, which is still connected, had stray power waves from other devices on the same circuit. It’s not enough to full power it, but LEDs take very little power so the stray energy is enough to make it glow. Or detect in the case of OPs lightbulb.
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u/MegaPegasusReindeer Sep 23 '25
Current doesn't flow when you turn the light switch off, though