An electric motor, comprising a shell for a rotor, which is closed by a cover provided with a hole for the passage of a motor shaft; the cover accommodates and supports sliding contact brushes for a commutator for supplying power to the rotor, a sensor for detecting the rotation rate of the rotor, and connections for signal transmission and power supply of the sensor. The sensor and its connections for the transmission of its signals and for supplying it with power are accommodated in a receptacle, which in turn is then inserted in a complementarily shaped seat in the cover.