Select 120 V Metered and Switched PDUs feature two input power cords and an automatic transfer switch (ATS). Network managers can plug the PDU's cords into two separate power sources. Depending on the desired level of power protection, the two sources can be two UPS systems, two generator-supported utility wall outlets, or one UPS system and one generator-supported utility wall outlet. When the primary input power source is normal, the PDU uses it to power connected equipment. If power fails or voltage drops below acceptable limits, a highly-reliable mechanism within the ATS automatically switches to the secondary input source to power connected equipment. The features allow managers to increase network availability by providing equipment with a redundant, backup source of power.