| 摘要 |
The invention relates to a switch for controlling the power to be fed to an electric motor of an electrical hand tool, which comprises a power supply connection, a motor connection, a controllable semiconductor connected between the motor connection and the power supply connection, a control circuit for controlling the semiconductor, and a safety circuit, wherein the switch comprises a cumulation circuit which is adapted to repeatedly measure a quantity prevailing in the switch or in its vicinity, assign a count value to the measured value of the quantity, cumulate the count values and generate a signal when the cumulated count value reaches a predetermined value. As a result of these measures the prior history of a component is included in the assessment of whether a situation is occurring which threatens the quality of this component.
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