Electrical control devices

An electrical control device comprising a base member, an elongate support member mounted to be movable transversely of its length with respect to said base member, biasing means to bias the support member against movement away from a null position in one direction transversely of its length, and a potentiometer comprising an elongate resistive member supported by and extending along the length of the support member and a sensing electrode which can be applied to the resistive member at a position intermediate its ends when said ends are connected to opposite respective poles of a voltage source to tap off a voltage which is selectively variable by varying the position along the support member at which the sensing electrode is applied to the resistive member, said resistive member being so arranged with respect to said support member that application of the sensing electrode to the resistive member tends to bring about movement of said elongate member with respect to said base member in said one direction, in opposition to said biasing means, and the device also comprising position pick-up means having a first part connected to said support member and a second part connected to said base member, said parts being arranged and connected to generate an electrical analog signal dependent on the position of said support member with respect to said base member, and the device also being provided with means for generating a predetermined response when said support member is moved from said null position through an initiating threshold position against said biasing means and for terminating said predetermined response when said support member is ruturned from beyond said initiating threshold position towards said null position through a termination threshold position.