Abstract: In an information recording/reproducing apparatus for recording/reproducing a digital audio signal on/from a magnetic medium, a modulator/demodulator for modulating/demodulating the digital signal by offset quadrature phrase shift keying (O-QPSK). This technique is particularly applicable to the multi-layer recording of video and audio signals in a video tape recording/reproducing system and has the advantage of avoiding interference between the recorded digital audio and video signals at the time of reproduction.

Abstract: In an optical disk player, such as for a magnetooptic player, wherein the data recorded on the optical medium are at recording at such high densities then intersymbol interference causes the peaks of the readback signals to become closer together resulting in phase errors. A transition selecting means is operative to select a transition indicated by the readback signal or a substitute transition indicated by a timed delay means generates a signal based upon the immediately preceding transition received from optical medium. Various embodiments of the invention are illustrated.

Abstract: A reading circuit used for a floppy disk unit capable of reading data by converting data stored upon the surface of a floppy disk in the form of magnetic variations of a residual magnetism into voltage variations by using a magnetic head. While one of the voltage signals read by a magnetic head is differentiated by a differentiating circuit with a predetermined differential property, the other voltage signal is supplied to a level slicer and is output after being converted into rectangular pulses at a predetermined threshold value. The pulse signals are delayed in accordance with a phase shift period caused by a differential of a differentiating circuit. The delayed signals are then delivered to a comparator, which detects a signal output from the differentiating circuit by performing a comparison, so as to activate the comparator intermittently. The pulse signals, a peak value of which is detected by the comparator, are shaped by a pulse shaping circuit, and are output.

Abstract: A prewrite compensation circuit for selectively delaying the writing of non-zero bits of data streams to disks of a hard disk drive. The hard disk drive includes a write circuit for writing the non-zero bits to selected portions of selected disk surfaces and selected write delays are effected by a variable delay circuit that receives the data stream from a shift register through which the data stream is passed. The amount of delay is determined by a delay word entered into a latch connected between the variable delay circuit and a RAM in which delay words are stored at addresses selected for each delay word in relation to the pattern of bits of the data stream surrounding each non-zero bit, the disk surface to which each data stream is to be written and the portion of the surface to receive the data stream.

Abstract: Digital audio and video signals are recorded on successive tracks which extend obliquely formed on a video tape, and reproduced therefrom by reproducing heads which are movable in a direction transverse to the tracks by means of a bimorph device so that a plurality of tracks, corresponding to one field video and audio signals, are skipped in a variable tape speed mode. Tracks provided for the audio signal are arranged at opposite ends of the video tracks. In a mode where the head skips one field, the signal amplitude level of the audio signal reproduced from one end portion of the audio tracks is controlled so as to be gradually reduced and a signal amplitude level of the audio signal reproduced from the other end portion of a different field track portion is controlled so as to be gradually increased so that cross-fading thereof is effected.

Abstract: In a disk drive providing amplitude sampling data detection, the amplitude of an analog read back signal is sampled at data clock intervals. The resulting analog values are converted to digital equivalent values. The digital equivalent values are each compared to an expected digital values that is representative of the data that was originally recorded on the disk, to thereby generate a different value. The resulting collection of difference values are magnitude segregated, and then stored in a plurality of registers, for later use in providing a histogram that is a measure of the disk drive's read error rate.