This Hammer Switch is 16A-125V (Replaces Bosch 1617200109, 1617200091 and 1619P10396) and is used in Bosch rotary hammers.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.