In article ,
larkim wrote:
Just curious, why do most wired doorbells need a transformer, with the
associated hassle of wiring from a mains source to the tranformer and
then to the bell, when they could just as easily use a 9V battery in the
sounder unit instead?

You won't get a loud sounder *and* decent battery life from a 9 volt
battery.

Mains bells also give the possibility of an illuminated bell push.

It's really hardly any more work to fit a transformer if using a cabled
system - and it's then forget time for many many years.

--
*When a clock is hungry it goes back four seconds*

Dave Plowman London SW
To e-mail, change noise into sound.