On Thu, 04 Oct 2012 13:52:21 +0100, Dave Plowman (News) wrote:

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.

We had one of those old Friedland things with the 4.5V battery and it was
plenty loud enough.
Due to old age (the bell) and difficulty in getting batteries, we no use a
wireless thing.
If I could get another 4.5V one I'd use 4 Eneloops in it - almost zero
running cost and should last a couple of years on a charge.
--
Peter.
The gods will stay away
whilst religions hold sway