Abstract: Apparatus for correcting or compensating for the tracking error of the pivotally mounted (1) tone arm (23) of a phonograph includes a first intermediate member (9) to which said tone arm (23) is pivotally (1) connected, a second intermediate member (12) which is rotatably connected to the first intermediate member (9) by a belt (18) and pulleys (13) which are sized in such a way that a photodiode source (21) and a photodiode detector (22) both carried by the second intermediate member (12) will tend to be indirectly moved by a motor to maintain them substantially constantly in register with a point on the tone arm (23). A slotted mask (24) carried by the tone arm (23) is interposed between the source (21) and the detector (22) and its slot defines a central "null" position in which said motor will not be driven when the required relationship exists. Deviation in either direction will cause the motor to be driven to re-establish this relationship. An insignificant maximum tracking error below 0.1.degree.

Abstract: A lockstitch sewing machine has, in addition to stitch forming instrumentalities (22, 24), a needle thread control arrangement (32) by which the tension in the needle thread (T2) is controlled during stitch formation. In addition, said arrangement (32) ensures that each formed stitch is drawn into the body of the workpiece, by pulling on the thread while it remains clamped by thread clamping means (200, 202). This pulling takes place in the early stages of the formation of the next stitch so that, at the end of the machine stitching cycle, the final stitch is not set by this arrangement (32). Instead, electrically actuated stitch setting means (220 to 226) is provided operable in response to an "end of cycle" signal supplied by control means by which further "end of cycle" functions (e.g. release of a presser foot (36) and of the thread clamping means (200, 202) are also controlled.