Electricians often speak of AC and DC which are acronyms that stand for Alternating Current and Direct Current. Residential and commercial electrical service is delivered as AC current. Most electrical devices like radios, TVs, phones, tablets and computers require DC to function. Because of this requirement, devices that require DC usually have a built-in rectifier or include a wall plug adapter to convert the AC voltage to DC voltage. Desktop computers have a power supply built-in which converts the AC voltage to the necessary DC voltages required by the computer.