Products in this family are component-level control devices used to construct equipment that converts AC utility power to a DC form, typically at a much reduced voltage. Devices which incorporate the primary switching element for the system and those which do not are both included. Due to the high ratio of input to output voltages and need for isolation commonly encountered in such systems, they are often used in conjunction with an external transformer. While use of custom transformers for this purpose is common practice, a variety of stock products intended for such use are available, under the heading of Switching Converter, SMPS Transformers.