The Wagan Tech Smart AC 150 USB II Power Inverter is portability at it's best. The Smart AC is powered from a 12 volt DC source and provides 120 volts AC 60Hz through two North American standard outlets to AC appliances up to 150 watts. The AC waveform is a modified sine wave (MSW) which approximates the sine wave of household electrical service. An attached DC power cord connects to a 12 VDC cigarette lighter socket. There is a USB power port that can be used to charge cell phones, PDAs and MP3 players. Safety features include automatic shutdown in the event of overheat, overload, under voltage and over voltage conditions.