Control device, in particular in the form of a frequency converter or a servo regulator, with a safe-torque-off function for an electric motor, the control device comprising: - a first actuator signal terminal to which a first actuator signal can be applied, and - a second actuator signal terminal to which a second actuator signal can be applied, wherein the control device is characterized by: - a power semiconductor (insulated-gate bipolar transistor, IGBT) for generating a high-frequency operating voltage for the electric motor, - first transmission means to generate a respective output signal in response to an input signal only if an associated supply voltage is provided, wherein a respective power semiconductor (IGBT) is controlled by an associated output signal, and - a supply voltage generator unit to generate the supply voltage for the first transmission means in response to the first and the second actuator signals (U1, U2) only if the first and the second actuator signals (U1, U2) each signal an operating condition, so that the power semiconductors (IGBT) are allowed to generate the high-frequency operating voltage for the electric motor only in the operating condition, the supply voltage generator unit comprising: - an oscillating circuit to generate an oscillating signal at an oscillating signal output only if an oscillating circuit supply voltage is present, wherein the oscillating circuit supply voltage is present only if the second actuator signal indicates the operating condition, - a second, in particular electrically isolating, transmission means which is connected on the input side between the first actuator signal terminal and the oscillating signal output, - an amplifier circuit to amplify a signal on the output of the second transmission means and to output an amplified signal, - a decoupling circuit to filter the amplified signal in that a constant component is removed from the amplified signal and to output the filtered signal, and - a rectifier to generate the supply voltage for the first transmission means from the filtered signal. - a first actuator signal terminal to which a first actuator signal can be applied, and - a second actuator signal terminal to which a second actuator signal can be applied, - a power semiconductor (insulated-gate bipolar transistor, IGBT) for generating a high-frequency operating voltage for the electric motor, - first transmission means to generate a respective output signal in response to an input signal only if an associated supply voltage is provided, wherein a respective power semiconductor (IGBT) is controlled by an associated output signal, and - a supply voltage generator unit to generate the supply voltage for the first transmission means in response to the first and the second actuator signals (U1, U2) only if the first and the second actuator signals (U1, U2) each signal an operating condition, so that the power semiconductors (IGBT) are allowed to generate the high-frequency operating voltage for the electric motor only in the operating condition, the supply voltage generator unit comprising: - an oscillating circuit to generate an oscillating signal at an oscillating signal output only if an oscillating circuit supply voltage is present, wherein the oscillating circuit supply voltage is present only if the second actuator signal indicates the operating condition, - a second, in particular electrically isolating, transmission means which is connected on the input side between the first actuator signal terminal and the oscillating signal output, - an amplifier circuit to amplify a signal on the output of the second transmission means and to output an amplified signal, - a decoupling circuit to filter the amplified signal in that a constant component is removed from the amplified signal and to output the filtered signal, and - a rectifier to generate the supply voltage for the first transmission means from the filtered signal. - an oscillating circuit to generate an oscillating signal at an oscillating signal output only if an oscillating circuit supply voltage is present, wherein the oscillating circuit supply voltage is present only if the second actuator signal indicates the operating condition, - a second, in particular electrically isolating, transmission means which is connected on the input side between the first actuator signal terminal and the oscillating signal output, - an amplifier circuit to amplify a signal on the output of the second transmission means and to output an amplified signal, - a decoupling circuit to filter the amplified signal in that a constant component is removed from the amplified signal and to output the filtered signal, and - a rectifier to generate the supply voltage for the first transmission means from the filtered signal.