Abstract: A system is disclosed for positioning an instrumentality over a predetermined range in response to a digitally coded position signal. To effect desired adjustments between digitally achieved positions, algebraically adjustable signals are subtracted from an analog position signal obtained from the digitally coded position signal.

Abstract: A drive mechanism for reciprocating a sewing machine needle bar endwise from an actuating crank is disclosed in which the lateral stud on the needle bar to which the drive link is connected is fitted with a ball bearing slidably constrained in a guide slot formed parallel to the path of needle reciprocation in a stationary guide frame. The forces and reactions occasioned by alternate acceleration and decelleration during each needle bar stroke will cause the outer race of the ball bearing to engage first one side then the opposite side of the guide slot during each stroke thus turning the bearing in opposite directions and distributing the wear.