BX500CI - Is it possible to disable power outage beep?

[Stoat13]

I've recently purchased a BX500CI UPS, and I'd like to know if it's possible to disable the power outage beep.
For those not familiar with the model, this UPS does *not* have a USB port or any means of connection to a PC, so I can't use PowerChute or any other software to communicate with the UPS.  There is no "mute" button.

The only change of settings explained in the manual is the procedure for switching between the 3 sensitivity modes using the ON/OFF button. I have tried all 3 sensitivity modes on the offchance that one of these disables the beep, but this doesn't solve the problem.

The only buttons on the unit are ON/OFF on the front and reset on the back. Is there a sequence of using these buttons which will have the desired effect? Unfortunately I have no means of "communicating" with the device.

Any suggestions gratefully received!