This is single 9 V Battery powered back blood cleaner / electrifier device that has input voltage of 33V dc from single 9v dc battery. Fits small enclosures of 3.8x2.4x.9 inch. Portable to wear on the go. I omitted power checking LED circuit as I can feel when the battery gets too low in power. I get fairly strong tingle all the way down to 10V dc. The board size is large enough to fit 2 zener diodes and one 22uF capacitor and jumpers to LED. Mounting this LED on a small case is more of a challenge due to limited space.