Abstract: A magnetic recorder including a playback circuit for decoding a ternary waveform digital data signal is disclosed, wherein positive and negative threshold levels, used to distinguish between signal levels representative of data ones from signal levels representative of data zeros, are automatically adjusted to compensate for occasional reductions in overall signal level that can occur due to dropouts and modulation noise on the magnetic medium. Two sample and hold units are used to generate an output signal whose amplitude reflects only those signal levels that are greater than some minimum absolute value. This output signal is filtered and then used to generate the compensated positive and negative threshold levels.
Abstract: A circuit for suppressing the effects of excessive highlights is automatically enabled in response to highlights in the viewed scene which exceed a given threshold. The circuit is used in combination with a special pickup tube or tubes which include excessive highlight protection elements and a corresponding mode of operation. The circuit allows the continuous operation of the pickup tubes with improved resolution at a heretofore prohibitive, but preferred, high voltage level (e.g., 950 volts), rather than the generally accepted and recommended operating level (e.g., 750 volts) therefor, while prolonging the lifetime of such tubes. Detector means generates the circuit enable signal in response to the presence of highlights in excess of the given threshold. Control circuit means are conditioned thereby to drive the tube into the corresponding mode of operation during the line flyback period corresponding to the horizontal blanking interval.