CyberPower’s CP900AVR has an easy-to-use interface with just two buttons (electric power on/off and mute) and 4 indicator lights (showing if the device is turned on, in the event the battery backup kicks in, when AVR is activated, and when there’s a power overload) about the entrance with the unit. https://raymonds2hhi.bloggazzo.com/35275171/battery-ups-9ah-12v-katzuni-kz12v9-no-further-a-mystery