The alarm in your power supply and battery backup unit will beep if the battery is running low on power and needs replacing. The beeping sounds becomes more frequent as the battery drops down to a critically low level.
Power Supply with Battery backup indicator lights and alarm sounds.
The following displays are present on the front of the unit:
The following list describes the different types of audible alarm sounds you might hear:
Alarm Silence Function
NOTE : You should only silence alarms when absolutely necessary as they are designed to alert you when your battery is in need of replacement, missing or running low and will soon be flat.
Feel free to see link below for the whole PDF details: