Abstract: Apparatus for effecting the technique includes a subtraction circuit for producing a difference signal by subtracting successive words of the serial bit stream forming the digital signal. A comparator circuit compares the difference signal to a predetermined maximum slew rate limit signals. If the difference signal is greater than the maximum limit signal, then subtraction and comparison is repeated, after shifting the successive words of the digital signal by one bit. This process is repeated until, when the difference no longer exceeds S, synchronization is assumed.

Abstract: A closed loop circuit corrects digital data baseline shift resulting from perturbing interferences. Samples of the signal amplitude are stored at each clock time; and a correction signal is derived from the stored information. The correction signal is subtracted from the data signal to produce a resultant signal that is devoid of baseline shift, such resultant signal being also used to control clock regeneration in a phase locked loop.

Abstract: An electrically conductive element is employed in proximity to a thin film magnetic structure. The conductive element has current applied to it which is just sufficient to maintain, by field coupling between the thin film structure and the conductive element, the given magnetic orientation of the thin film structure, this occurring despite the application of a signal field tending to reorient the magnetization of the thin film structure. Such current is, therefore, the analog of the applied signal field and, since the magnetization of the thin film structure, by virtue of induced magnetic feedback, does not appreciably change direction, harmonics of any signal field applied to the thin film structure, and noise, are not manifested in the current analog.

Abstract: A high Q magnetic playback head applies its developed signal to the input of a voltage mode circuit. To facilitate equalizer design, the head is resistor-damped. While mere resistor damping reduces the Q of the head, it does so at the expense of the signal-to-noise ratio (SNR) of the head-and-amplifier circuit. To maintain SNR substantially without change, the amplifier employs a large resistance to which negative feedback is applied so the resistance appears as an effective resistance equal to its actual value divided by the amplifier gain. The value of this effective resistance is made to equal the magnetic playback head inductive reactance at the point of resonance, thereby reducing the head Q to approximately 1, and equalizer design is made easier.