On Thu, 22 Oct 2020 06:28:39 -0700 (PDT), "
wrote:

What about installing another light-draw chime just inside your door? Activating the button would trip both. Just put it in series with the bell.

That was another thought Peter (and was suggested elsewhere), maybe a
electromechanical buzzer so they hear the buzzer directly and also any
reverberations that travel though the frame etc.

KISS

Quite, but the issue with the above is that I'd need to get lucky and
find something that would work itself and allow the existing bell to
ring, especially when it's already running on a reduced voltage (4.8V
of Ni-Mh rather than 6V of alkaline).

That's why I was trying to isolate the existing bell functionality and
leech some power off that to run an auxiliary sounder.

Cheers, T i m