Switchmode is an electronic power control technique that allows DC or AC power to be converted from one form to another in a fairly efficient way and without the need for bulky transformers. The underlying principle exploits the fact that the bulk needed for a transformer is smaller if it is operated at a high frequency. The switchmode technique electronically chops up the incoming power source at a high frequency before passing it through a transformer to achieve whatever voltage transformation is required. The output from the transformer is converted back into DC by a rectifier and a filter; which is intended to remove the high frequency components. Control is achieved by varying the width of the AC pulses; with the output filter acting as an averaging circuit. This is the basis of the Pulse Width Modulation control method - PWM. Advantages include smaller size and weight than alternatives, but the high frequency switching has the potential to cause interference problems with radio systems or video circuits. Circuit complexity can degrade reliability, but this may be offset by gains due to lower operating temperatures.