The active version of OLTC uses a reactor built for continuous loadings, such as a blocking autotransformer, and uses the bridge area as a service area.
There are two basic designs for OLTC. For high voltage and power, the diverter design includes both a pump selector and a separate diverter switch (also called an arcing switch). Switching arc can occur in oil or inside the vacuum bottle.
For low power measurements, the fixed design uses a selector switch (also known as an arcing tap switch) that integrates the role of the switch and the selector switch.