the source of electrical power (power outlet). In North America, this source is generally 120 volts AC, 60 hertz. In Japan, the source is generally 100 volts, 50 or 60 hertz. In the United Kingdom, the source is 240 volts, 50 hertz. In Europe, the source is generally 220 volts, 50 hertz. In addition, some equipment is operable off of DC sources, such as batteries.