The external battery backup unit, EBU-120, is an optional compact device that is capable of connecting external battery with a switch to reach power redundancy. That is, EBU-120 is rendered a bridge between battery and switch. Upon power failure, the external battery actuates automatically with supplying 12V DC power. After power source from adapter is restored, EBU-120 would change over the power source from battery to adapter and recharge the battery immediately.
EBU-120 also designed with a protection mechanism to avoid damage due to incorrect installation or operation, such as polarity reverse or short circuit. Moreover, the condition of battery is fairly clear via LED indicator showing its immediate status.