Automatic control system having manual control engageable at will

In a device for exercising control over a further member, which further member may be remotely located from said device, wherein said device includes an external power supply for exercising said control, the combination of a linear stepping motor and a remotely adjustable pulser for directing the exercise of said control, a coupling means between said linear stepping motor and said external power supply which is laterally movable and retained from rotational movement by sliding friction means, and a manually operated means which is capable of overcoming the friction forces of said sliding friction means restraining said coupling means and thus directing the exercise of control.