Abstract: In a tape drive system, a dynamic brake control circuit provides dynamic braking for slowing and stopping an associated tape reel and motor system in the event of a power failure. Upon sensing a power failure, the electrical energy stored in a capacitor supplies electrical energy to enable the control circuit, which in turn supplies a controlled conductive path for the flow of a dynamic braking current due to the back electromotive force signal generated by the motor, to effect the controlled dynamic braking of the drive motor to a stop.

Abstract: A noise immunity circuit incorporates a first channel for tracking a train of periodic sync pulses and for locking a window to said pulses for rejecting spurious noise signals. A second channel senses when the sync pulses are displaced in phase and establishes a new rephased window that is in phase with the displaced sync pulses.

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.

Abstract: An optical sensing circuit useful for detecting the end of a moving tape in a tape transport includes a light source and a light sensor which are closely spaced across a gap. The radiation output of the light source is modulated at a selected frequency which is determined by the operating frequency of a frequency detector. In the absence of a light obstruction, such as passage of the tape in the optical path between the light source and the light sensor, the modulated output from the light source is detected by the sensor. The processed signal from the sensor, which is characterized by the modulation frequency, is applied to the frequency detector. The detector recognizes only those signals having the modulated frequency, and does not respond to signals of different frequencies, which may result from impingement of other radiation than that from the light source on the photosensor.

Abstract: An apparatus for controlling the phase of a video data signal to effect color correction includes a video data memory and memory control circuit. Interlaced write and read portions of the memory cycle are selectively spaced in time within a memory read/write cycle to enable shifting the read portion by a selected fraction of the memory read/write cycle without affecting the write portion, whereby color correction is achieved.

Abstract: A frequency measuring circuit measures the period between successive pulses of an input signal and converts the pulse count to a measured frequency value. The measured frequency signal is filtered to eliminate spurious noise and a variable threshold is generated by comparing the measured frequency and the filtered frequency. Only frequency signals qualified by the variable threshold are accepted as valid and provided as the output.