Abbreviation for "Alternating Current". The form of electricity coming from the power plant to your electronic equipment. In North America, alternating current changes it's direction 60 times per second, or at 60 Hertz. While it is changing directions, it moving in a sine waveform. The current does a 180 degree turn in one direction, then another 180 degree turn in the opposite direction. This looks similar to the tilde (~) symbol on your computer keyboard.