My grandmother's door bell stopped working (one that's mains powered, via a "hard of hearing" box which also makes a series of lights flash in her house), so I bought a new "mains powered" 8V bell from B&Q. It doesn't work properly though; it rings once when you press the button in, and once again when you release it. I'm guessing the bell wants AC but is getting DC. It doesn't say on the packaging or the instructions whether it wants AC - only "8V 1 amp". Are most mains powered bells AC?
The old one was designed to be battery powered by two 1.5V "D" batteries and the electrician who fitted the "hard of hearing" box and flashy lights just replaced the batteries with a cable from there, so I guess it could have been more than 3V and it burned out after a few years. Sadly I can't find my multimeter to see what it's actually outputting.
alex.