This is a Vertex battery power supply. After purchasing it new, I set it up on a pedalboard once and confirmed it was working at home, but I haven't used it otherwise. It's a power supply that can accommodate four 9V batteries. This power supply requires a separate 9V battery to act as a switch to operate the entire unit. Turning off the master power battery turns off the entire unit, preventing the four batteries in the unit from draining. I think it's ideal for power noise countermeasures. I will also include a connector for the 9V battery used for the master power. Although it is in good condition, it is still a used item, so please understand that it is non-refundable and non-returnable.