In electronics, a
center tap (
CT) is a contact made to a point halfway along a winding of a
transformer or
inductor, or along the element of a
resistor or a
potentiometer. Taps are sometimes used on inductors for the coupling of signals, and may not necessarily be at the half-way point, but rather, closer to one end. A common application of this is in the
Hartley oscillator. Inductors with taps also permit the transformation of the amplitude of
alternating current (AC)
voltages for the purpose of power conversion, in which case, they are referred to as
autotransformers, since there is only one winding. An example of an autotransformer is an
automobile ignition coil. Potentiometer tapping provides one or more connections along the device's element, along with the usual connections at each of the two ends of the element, and the slider connection. Potentiometer taps allow for circuit functions that would otherwise not be available with the usual construction of just the two end connections and one slider connection.