A variation of the carrier frequency method, used for indicating the oscillations of a torsion pendulum, is described. In order to avoid additional torques caused by contact wires the transmission of the modulated carrier frequency is performed by an air core transformer consisting of two movable primary coils and two stationary secondary coils. It is a special feature of this arrangement that the coupling of primary and secondary coils does not depend on the angle of twist, provided this angle remains within a range of about 20°.