A ferrite phase shifter is described in which the switching circuit is arranged to apply a complementary setting pulse to a latching wire (4) of a toroidal ferrite phase shifter (2) before a resetting current pulse is applied by means of a latching wire (6). A new phase state is then set by a normal setting pulse applied to the latching wire (4). The complementary setting pulse is of a voltage sufficient to bring the magnetisation state of the phase shifter to an unsaturated magnetic state. This may be achieved by applying a complementary setting pulse of a voltage which together with the voltage of the previous setting pulse adds up to a constant amount. Alternatively, the magnitude of the complementary setting voltage may be determined on an empirical basis in order to reduce the phase error in any subsequently set phase. This may result in the unsaturated magnetic state varying in dependence on the previously set state.