1. In an electrical connecting device for transmitting electrical energy from a first part to a second part, said parts being displaceable relatively to one another, comprising, a primary coil connected to said first part, a secondary coil connected to said second part, said coils having same axis of symmetry, a magnetic circuit with an air gap, and said magnetic circuit consisting of magnetic plates, means for displacing one of said parts relatively to said another part whereby to inductively couple said coils which are integral with said parts respectively when said coils have been properly displaced, and said inductive coupling being achieved irrespective of the relative angle of said coils about said axis of symmetry, the improvement of having slots formed in said magnetic circuit for housing said primary and secondary coils respectively, said coils being electrically connected as the rotor and the stator of a polyphase asynchronos motor, and stop support for preventing relative rotation between said displaceable parts of said connecting device.

8. An electrical connecting device for transmitting electrical energy and electrical signals, said device operating in a corrosive medium such as seawater, comprising a first part and a second part which are displaceable relative to each other along a common axis of symmetry, a first and a second primary coils connected to said first part and said coils being independant from each other, a first and a second secondary coils connected to said second part and said coils being independant from each other, a first magnetic circuit with an air gap and a second magnetic circuit with an air gap, said magnetic circuits being respectively associated with said first and second primary and secondary coils respectively, means for displacing said first and second parts with their integral coils and magnetic circuits, relatively to one another, and said first primary and secondary coils, as a first set of coils, so as said second primary and secondary coils as a second set of coils, being inductively coupled through said air gaps respectively of said magnetic circuits, when said one part is displaced along said axis of symmetry into said other part, the coils of one set being arranged so as to produce a radial rotating field perpendicular to said axis whereby, to transmit said electrical energy, the coils of the other set being arranged so as to produce a fixed field whereby to transmit said electrical signals, stop support for preventing relative rotation between said displaceable parts and protective coating in said air gaps for protecting said magnetic circuits against corrosion by seawater.