The behaviour of a single-phase series-transductor circuit, with a low-impedance signal source, is examined analytically and experimentally for various load conditions; these include a. c. inductiveresistive loads, rectifier-fed inductive-resistive loads, and rectifier-fed loads with capacitance smoothing of the bridge-rectifier output voltage.Account is taken of the finite permeability of the core when considering the circuit sensitivity with self-excitation feedback. The influence of the load on the control-circuit time-constant is also discussed.The unsatisfactory behaviour of transductors with rectifier-fed inductive-resistive loads is explained and methods of effecting an improvement in performance are suggested.