The mUPS is a smart PoE injector with a 12 V battery connector. It works just like a Gigabit PoE injector, but when power is lost, it switches over to the 12 V battery. Even if your power source is 28 V, the connected RouterBOARD will not reboot when the power source is lost, it will switch over to the 12 V battery transparently.
The LEDs indicate DC line or battery usage, the charging of battery and low battery level (<50%). In RouterOs it is possible to detect when running on battery power by monitoring the input voltage with scripting, since the voltage will change without a RouterOS reboot.
The mUPS is a simple and compact device to make your network more reliable, or for situations where stable power input is not available, like solar or automotive installations.
Note: 12 V battery not included and must be mounted separately.