Another unusual feature is the use of magnetic cores not only for memory but also as logic gates. These logic cores have 1, 2 or 3 input windings, a trigger (read) and an output winding. Depending on their polarity, current pulses in the input windings either magnetise the core or cancel each other out. The magnetised state of the core indicates the result of a boolean logic function. Two clock phases designated alpha and beta are used to trigger (reset to zero) alternate cores. A change from a one to a zero produces a pulse on the output winding. Cores which receive alpha trigger pulses (alpha cores) have inputs fed from gates which are triggered on the beta phase (beta cores). Transistors were expensive at the time and each logic gate requires only one to amplify the output winding pulse; however a single transistor drives the inputs of a small number of (typically 3) other cores. If more than 3 inputs are to be driven, up to two more transistors can be driven by each core.