Power switching involves routing power through a switching regulator. Whereas a linear regulator maintains a continuous load current to create a constant load voltage, a switching regulator maintains a constant current flow by chopping the input voltage into smaller chunks or energy and sending them one at a time into the output.

Industrial electronic systems often use power switching because switching regulators are more efficient — offering 70% to 95% efficiency rather than 40% to 70% efficiency of linear regulators. They can allow for smaller, lighter and quieter systems. 

Power switching can be direct or indirect. Direct power switching sends the power line directly through the switch. Direct power switching is most common for industrial electrical systems that use DC power sources. It is also the most common method for currents of 15 amps or less and AC power sources of 120 volts or less.

Indirect power switching, on the other hand, keeps the power line separate from the control panel. For this reason, it is often used with higher voltage and amperage. In this setup, instead of going directly through the switch, the power line runs through a contactor, mechanical relay or solid-state relay. The control switch is separate — it may be local, separate or connected via another relay. 

A power distribution unit often has auto-transfer capabilities that allow for automatic switching.