Bob Eager wrote:

I note something in the FAQ on the APC website, so when I get a chance
I'll shut everything down on one of them and give it a go.

Some of the cheaper APCs (backups rather than smartups?) have a combined
on/off button, rather than separate on and off buttons; with those you
give it a 2 second press to silence and have to be careful not to press
it too much longer after it gives a double confirmation beep, otherwise
you can accidentally turn it off.