(n): the side upon which the use of a thing depends (usually the most prominent surface of an object)
(n): the control on a radio or television set that is used for tuning
(n): a mechanism that controls the operation of a machine
(n): the circular graduated indicator on various measuring instruments
(n): a device for showing the operating condition of some system
(n): a disc on a telephone that is rotated a fixed distance for each number called
(n): a switch that is used to select among alternatives
(v): operate a dial to select a telephone number
(v): handle and cause to function
(v): choose by means of a dial
(v): pick out, select, or choose from a number of alternatives
Laid in reverse.