A variable reluctance transducer includes a C-shaped assembly (10) defining a magnetic circuit, one limb of the C being longer than the other. The assembly (10) is arranged with its limbs on opposite sides of a movable member (16). A winding (14) linked to the magnetic circuit is connected to a discriminating circuit including an integrator (A, R, C) having a variable bias circuit (D1, D2, R3, R2, C2, C2, A2, R4) which ensures that the peaks of the integrator output are in a predetermined relationship to a reference voltage. A comparator (A3) compares the integrator output with the reference voltage.