Dunno, but I do have some non-answers to your question: you can set the input sensitivity, the transfer voltages (i.e. how far out of spec the voltage has to be before it disdains the mains) and you can turn off the beeping.

With Linux apctest, that's "SENSITIVITY L", "LOTRANSFER 196", "HITRANSFER 265" and "BEEPSTATE N" in /etc/apcupsd.conf.

Peter