DIGIPOWER 4.2-Amp (21 Watts) 4-Port USB Wall Charger with InstaSense(TM) Device Recognition Technology is the fastest way to charge your devices. InstaSense (TM) automatically senses the power requirements of any smartphone or tablet and delivers the fastest possible charge. Compact size with folding plug and world wide voltage for easy travel. Advanced protection to safeguard against: over voltage, over current and short circuit.