Yes, it can happen that you want to load their device with USB port, or even have the trouble afraid the computer or the laptop to turn on so that power to the USB comes when something is at all close (holiday !!!) , Here acts This one bedroom unit wonder, because USB plug in, charger into the wall socket and that's it, happy shop everywhere ;-) Ideal for my Sony MP3 player Walkman NWZ-S545 and designed for 1 million other USB devices have no own power supply.