Actuator for a flap or for a valve , with a brushless direct current motor , a downstream transmission , an actuation connection point for connecting the flap or the valve and with an electrical connector (AN) for connecting the actuator to an external control cable (SL), which is provided for the energy supply to the actuator and for providing the direction of rotation of the brushless direct current motor and which has a first and second motor cable (LY1, LY2) and an earth line (GND), wherein the brushless direct current motor can be driven in the first or second direction of rotation on the basis of a respective first or second motor voltage (UY1, UY2) applied to the first or second motor cable (LY1, LY2), wherein the actuator comprises a motor control unit with a signal evaluation unit (SA) and with a downstream control facility (SE) for the brushless direct current motor , wherein the actuator has a voltage supply unit , which is designed to provide a direct supply voltage (UP) for supplying power to the motor control unit from the first and/or second motor voltage (UY1, UY2), wherein the signal evaluation unit (SA) is designed to generate control signals (S OPEN , S Y1 , S Y2 , S Y1+Y2 ) assigned to the control device (SE) for the time that the first and/or second motor voltage (UY1, UY2) is applied to the first and second motor cable (LY1, LY2), and wherein on this basis the control device (SE) is designed to electrically actuate the brushless direct current motor in the assigned first or second direction of rotation, - wherein the signal evaluation unit (SA) has a digitisation stage (DIG) with a number of A/D converters (ADC) for converting the two motor voltages (UY1, UY2) into corresponding digital motor voltage signals (Y1, Y2), - wherein the signal evaluation unit (SA) has a digital mixer stage (SF) for generating in each case a beat signal (Y1 AC.R , Y2 AC.R ) from the digitised motor voltage signals (Y1, Y2) supplied on the input side and from a demodulation frequency (f o ), wherein the respective beat signal (Y1 AC.R , Y2 AC.R ) represents the effective value of the demodulated motor voltage signals, and - wherein the signal evaluation unit (SA) has an evaluation stage (BW), which is designed to generate the control signals (S OPEN , S Y1 , S Y2 , S Y1+Y2 ) for the downstream control device (SE) of the actuator from the two beat signals (Y1 AC.R , Y2 AC.R ). - wherein the signal evaluation unit (SA) has a digitisation stage (DIG) with a number of A/D converters (ADC) for converting the two motor voltages (UY1, UY2) into corresponding digital motor voltage signals (Y1, Y2), - wherein the signal evaluation unit (SA) has a digital mixer stage (SF) for generating in each case a beat signal (Y1 AC.R , Y2 AC.R ) from the digitised motor voltage signals (Y1, Y2) supplied on the input side and from a demodulation frequency (f o ), wherein the respective beat signal (Y1 AC.R , Y2 AC.R ) represents the effective value of the demodulated motor voltage signals, and - wherein the signal evaluation unit (SA) has an evaluation stage (BW), which is designed to generate the control signals (S OPEN , S Y1 , S Y2 , S Y1+Y2 ) for the downstream control device (SE) of the actuator from the two beat signals (Y1 AC.R , Y2 AC.R ). <EOS>