Abstract: A method and a circuit for protecting an electric motor and/or its trigger circuit against overload in the emergency-operation mode in a motor vehicle direct-current fan motor operated by means of pulse width modulation, in which the trigger circuit is designed as an emergency-operation controller, with a microcontroller preceding the motor end stage and with a comparator assembly for detecting overvoltages. Overload protection is assured at elevated battery voltage and at the same time when the emergency-operation controller is activated in response to malfunctions in the normal triggering of the electric motor. To that end, at least one overvoltage threshold (Us1, Us2) is defined; when it is exceeded, the power supplied to the motor is reduced or switched off.

Abstract: A method and a circuit arrangement suitable for performing the method are provided for protecting an electric motor (10) and/or its trigger circuit (12) against overload in the emergency-operation mode. The method of the invention and the associated circuit arrangement serve in particular to protect a motor vehicle direct-current fan motor operated by means of pulse width modulation, in which the trigger circuit is designed as an emergency-operation controller, with a microcontroller (16) preceding the motor end stage (22) and with a comparator assembly (14) for detecting overvoltages. The provisions according to the invention assure overload protection at elevated battery voltage and at the same time when the emergency-operation controller is activated in response to malfunctions in the normal triggering (12) of the electric motor (10). To that end, at least one overvoltage threshold (Us1, Us2) is defined; when it is exceeded, the power supplied to the motor is reduced or switched off.

Abstract: A central locking system for use in a motor vehicle includes a pressure source generating preferably an under pressure and an over pressure. The source is connected to a series of pneumatic control units each including a pressure chamber, a control element arranged in the chamber for movement between two control positions, an opening in the chamber communicating with a space enclosing a valve which normally closes the opening and the space being provided with a discharging nipple which is coupled via the subsequent series connected control units to an indicator device. The indicator device is arranged in the field of view of the car operator. In this manner, the operating condition of locking devices which are outside of view of the operator can be reliably checked.