Abstract: It is an eddy current speed reducer whose stator comprises a ring of coils 2 having their axes parallel to the axes of the speed reducer and whose rotor comprises two discs 3 framing the stator.The support for the coils is formed by a non-magnetic closed annular housing 9 containing the windings 6 of these coils and formed from two half-shells clamped axially one against the other by screwing flared pole pieces 7 on the cores 5 of the coils, these cores passing jointingly through openings 11 in the housing.A preferred application is to speed reducers developing relatively low braking torques.