Abstract: Disclosed is a monitoring circuit responding to different operational conditions of an electric motor. The circuit includes a measuring resistor connected in series with the stator winding of the motor to produce an actual load value signal. The actual value signal is applied to one input of a comparison circuit whose other input is consecutively supplied with three different nominal reference voltages corresponding to principle operational conditions of the motor, namely to the starting phase, to the normal operational phase, and to an overload. The source of the variable reference voltage includes switching transistor cooperating with a timing member and with voltage dividers adjustable from zero to a maximum nominal voltage value corresponding to the power supply voltage.

Abstract: The method of and the device for indicating the optimum adjustment of the effective length of bristles of a bristle roller in a floor cleaning appliance driven by an electric motor is based on the measurement of a voltage drop across a resistor connected in series with the electromotor; the voltage drop is applied to a switching circuit including two parallel branches of series connected switching diodes with light-emitting diodes so as to activate the light-emitting diodes when the voltage drop exceeds the bias determined by the threshold voltages of the switching diodes.