A differential effect of the angular displacements of control surfaces is often required in the case of aileron controls, viz., a movement whereby for a given angle of rotation the upwardly‐moved aileron shows a range of deflexion which is different, measured from the common neutral position than that of the downwardly‐moved aileron. Fig. 4 shows the position of the device if the neutral position of the aileron is moved upwards. Fig. 5 shows the same operation, but with the neutral position displaced downwards.