On Thu, 4 Oct 2012 04:14:13 -0700 (PDT), 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?

I presume there's a good reason, just I'm too much of a numpty to work it out for myself.

Probably because most (?) bell pushes have an internal lamp, so draw
current continuously. A battery wouldn't last very long!

--
Frank Erskine