The invention relates to an operating state circuit for actuating an inverter (3), which supplies an n-phase electrical machine (5) with an n-phase supply voltage via phase connections (4a, 4b, 4c), wherein n≧1, comprising an evaluation device (6) which is connected to the phase connections (4a, 4b, 4c) of the inverter (3) and which is configured to detect output voltages of the inverter (3) to the phase connections (4a, 4b, 4c) and to determine a speed of the electrical machine (5) on the basis of the detected output voltages, and an actuating device (7) which is coupled to the evaluation device (6) and which is configured to switch to an idle state or an active short-circuit in dependence on the determined speed of the inverter (3).