This chapter presents some transformer basics and provides design and construction techniques for a transformer that provides a high degree of isolation. One major drawback of using an isolation transformer is its size and weight. However, it may be the best solution overall when a transformer is required somewhere in the equipment, because it is the only transformer that can provide DC isolation and an efficient means of stepping voltage up or down. In a design example mentioned in the chapter where it is necessary to provide an isolation transformer for a load, it is determined that a 500-VA transformer rating is sufficient to run the load. In the example, the nominal input voltage is 120 V AC and the frequency is 60 Hz.