CyberPower’s CP900AVR has a fairly easy-to-use interface with just two buttons (electrical power on/off and mute) and 4 indicator lights (displaying when the unit is turned on, once the battery backup kicks in, when AVR is activated, and when there’s an influence overload) on the entrance on the unit. Picture: https://bydthailand93580.eedblog.com/36457282/getting-my-ups-battery-tester-to-work