Abstract: For transferring signals relative to an electric machine provided with a three-phase power supply cable with three phase conductors, there is applied a signal to be transmitted to a first point in the three-phase cable between anyone of the phase conductors of such cable and both of the other phase conductors taken conjointly, and a reception signal is picked up in another point in said cable between anyone of the phase conductors of such cable and both of the other phase conductors taken conjointly.Preferably, similar capacitors are associated with each of the phase conductors in the cable at each end thereof, a galvanic separation transformer being disposed between such conductors, and the transmitter and the receiver, respectively, and an inductance being disposed between such transformers and conductors.