How does the VISTA-128FBP supervise its backup battery and what does a battery trouble condition indicate?

The VISTA-128FBPT supervises the backup battery by monitoring for a low voltage state, which triggers a SYSTEM LO BAT display on the keypad accompanied by a beep once per minute (Page 60) [1].

On a Master Keypad, this condition is represented by the letter L in the partition status display (Page 24) [1].

A battery trouble condition indicates that the system's backup power is low and requires immediate service (Page 60) [1].

If the display shows LO BAT followed by a zone descriptor, it indicates a low battery in a wireless transmitter rather than the main control panel (Page 60) [1].

Note that while the system alerts for a low battery, the keypad does not specifically annunciate the total loss of system battery power (Page 68) [1].