4 ms·
Battery-powered smoke detectors will likely be running on DC so coil hum seems unlikely.
by na85 12y ago
Battery-powered smoke detectors will likely be running on DC so coil hum seems unlikely.
- bronson 12y agoUnless it has a switching converter or regulator. Even when running at high frequencies they'll often generate harmonics in the audible range. It can take a heck of a lot of effort to keep a circuit quiet and nonmicrophonic.