Abstract: In a helical scan recorder in which timing signals are recorded on adjacent slant tracks on magnetic tape, an automatic tracking technique for maintaining correct reproduce head to track positioning. The automatic tracking technique includes reproducing recorded timing signals from adjacent slant tracks on magnetic tape, producing first and second simultaneous repetitive reference signals which are coherent with the reproduced timing signals and which are 180.degree. out of phase with each other, simultaneously sampling each of the reference signals with the reproduced timing signals, selecting from the sampled reference signal the signals which are sampled in the mid-range of values thereof, and comparing the selected sampled reference signals and producing a tracking error signal if there is a difference therein.

Abstract: A system for controlling a pulse-driven dc motor includes a pulsed grounding switch, an inductor connected between the pulsed grounding switch and the armature of the dc motor, and a tracking circuit connected across the inductor. The control system further includes a variable resistor that provides a series path through the inductor for dissipating generated armature current from the motor. In operation, the resistance provided by the variable resistor depends upon the counter emf generated by the motor and upon transient voltages induced across the inductor when the pulsed grounding switch is periodically opened and closed. More particularly, the variable resistor provides minimal resistance when the back emf of the motor is low and provides increasing resistance as the back emf of the motor increases.

Abstract: In a tape transport apparatus, a first servo feedback loop is provided for correcting tape tension by adjusting the rotation of a tape reel in response to the sensed position of a tension arm that engages the moving tape. A second feedback loop senses the rate of change in the position of the tension arm and responsively damps the tension arm position changes by means of a lead circuit which causes a torque motor coupled to said pivotable arm to move in opposition to the tension arm position changes.