Abstract: A mains braking device for a line-powered power tool includes a circuit arrangement with a two-pole switch which switches between the motor mode and the braking mode. The inventive braking device further includes an electronic power circuit breaker or triac which is connected in series to the commutator motor of the power tool and with control electronics allocated to the triac. For the safe recognition and initiation of the mains braking mode, the control electronics is provided with devices for differentiating between the motor mode and the mains braking mode. The mains braking device is especially useful for power tools such as right angle grinders, hand-held buzz saws and the like which are provided with dangerous tools.