This cable is kinda fascinating - it has an integrated boost converter, so you can plug it into any USB port (from a computer, battery pack, etc) and it will give you a higher DC voltage! It's a handy way to power 9V powered devices with a center-positive 2.1mm DC barrel jack from a USB port. We also have a version that provides 12V, and if you just need a passthough cable, here's one for 5VDC.