Abstract: There is described herein a method of operating an extruder for thermoplastic material to automatically control the output of the extruder. The extruder includes a kneader screw, a hopper having a feed screw for feeding the thermoplastic material in dry particulate form to the kneader screw and an outlet feed screw for removing the plastic material in molten form from the kneader screw. Each of the screws is operated by a separate electric motor. The method includes monitoring the current of the motor for the kneader screw. Variations in the current indicate variations in the opertion of the kneader screw. Upon any variation in the current of the kneader screw motor, the speed of the hopper feed screw and/or the outlet feed screw is varied to compensate for the variation in the operation of the kneader feed screw and return the current to its original value.

Abstract: In an apparatus for detecting defects on capacitive video disc records, a pickup stylus spanning a plurality of information tracks is effectively swept over the recorded disc area by rotation of the disc. The stylus, upon encountering a convex surface defect, is lofted from the disc surface with a consequent reduction in stylus-disc capacitance. The change in capacitance is indicative of the stylus ejection distance and thereby releated to the size of the defect. Transducers monitor the radial position of the stylus and the angular position of the disc. Each time a disc defect generates a defect indicative capacitance change, the coordinates of the defect are recorded as well as the magnitude of the capacitance change.

Abstract: Horizontal synchronizing pulses are separated from a composite video signal and applied to a detector for producing an error signal representative of the timebase error of each pulse relative to a timebase reference having a period of approximately one horizontal line. Changes in the error signal are inhibited when the time period between pulses differs substantially from one line. Peak values of a given frequency component of the error signal are detected and averaged to provide an output signal manifestation representative of the frequency, amplitude and grouping of the timebase errors and which is relatively unbiased by pulses having a period substantially different from the period of the timebase reference. The apparatus may be used, illustratively, for quality control purposes and timebase error source identification in video disc mastering, replication and playback apparatus as well as for measurement of the effectiveness of timebase correction apparatus.