A rotary potentiometer (Pot) is a three-terminal device that employs a resistive element and a rotating contact to form an adjustable voltage divider. If only two terminals are used, one end of the element and the adjustable contact, it acts as a variable resistor or rheostat. Potentiometers are selected by the resistance value of the element, degree of rotation/number of turns, linear or logarithmic taper, power dissipation, number of ganged elements, resistive material and termination style. Some have built-in switch contacts.