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.

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.

Unless the customer buys the parts. eg MTS8

http://www.electrika.com/f/0150-wylex-09/index.html#9

part of DIN RAIL MODULAR DEVICES FOR USE IN + UNITS AND FLEXIBLE UNITS.

And what was the advice from Wylex technical sercices department (the
customer had a NH CU)?

The advice was, "it does not fit the CU, use a seperate enclosure next to
the CU".

--
Adam