of the direction in which the motor rotates a level selector 56a controlled by switch 54a operates similarly in respect of limiting the speed of the rear steering motor 54a the amplifier 60 generates a signal subsequently fed as described through the level selector 56 to initiate rotation of the front steering motor 22 the output of the amplifier 60 being proportional to the difference between a voltage obtained from the feedback potentiometer 28 and a demand signal obtained from a second level selector stage 64 since the motor acts to reduce this difference to zero subject to amplifier sensitivity and system errors the effect is to move the front wheels and so steer the car so that the front wheels point in a direction determined by the demand signal the demand signal comes essentially from a switch 62 which may take one of three positions the central position giving a demand signal of zero causing the front wheels of the vehicle to return to their central position and to remain pointing straight ahead regardless of the position or movement of the steering wheel and regardless of external forces which the operation of the motor 22 will resist the other two positions of switch 62 cause the demand signal to be derived from the master potentiometer 24 with normal and inverted polarity because of the inverting amplifier 66 respectively the level selector 64 functions in a similar manner to level selector 56 the limiting level in this case being set by a combination of a switch 66 and a potentiometer 68 in the clockwise position of switch 66 the output voltage of the master.