Available power varies among countries, but it is generally a three-phase, four-wire, 50/60 cycles per second (Hz) alternating current (AC) system. Three cables carry 240/120 V, and one neutral cable has no voltage. The supply voltage is 120 V/60 Hz in the United States, 220 V/50 Hz in Europe, and 240 V/50 Hz in the United Kingdom, Australia, and New Zealand.