CyberPower’s CP900AVR has an easy-to-use interface with just two buttons (power on/off and mute) and four indicator lights (displaying if the device is turned on, once the battery backup kicks in, when AVR is activated, and when there’s a power overload) within the front on the device. Image: Michael Hession https://simonppnkf.targetblogs.com/36750019/the-2-minute-rule-for-ups-battery-lithium