Superior Electric SW38B Power Tools Trigger Switch - (Eaton Style) 20/12A- 125/250V. Trigger Switch. This replacement part is sold individually. Switches are commonly replaced parts in power tools. A switch handles all on/off and variable speed functions. They also have a role in electric breaking; they can momentarily reverse electrical polarity. Because switches use mechanical internals, they tend to degrade and wear out over time, eventually requiring replacement.