The card reader includes a peak detector that detects a peak point of a reproduced signal according to a threshold. The peak detector applies, to a first peak value to be determined, a second peak value immediately before the first peak value, a third peak value, which is the second preceding peak value with respect to the first peak value, and a next peak value. When a difference between a first intermediate value, which is a value between the third peak value and the second peak value, and a second intermediate value, which is a value between the second peak value and the first peak value, is greater than or equal to a first difference value, the peak detector ignores a first threshold, and decides the first peak value after confirming that a digital value corresponding to the next peak value has exceeded a second threshold.

According to one embodiment, a magnetic disk device includes a magnetic disk including at least one servo zone that includes a first data storage track with a first servo pattern having a first frequency and a second data storage track with a second servo pattern having a second frequency, wherein the first data storage track is located closer to an outer diameter of the magnetic disk than the first data storage track and the first frequency is greater than the second frequency; a magnetic head that faces the magnetic disk; and a zone servo switching unit that switches a servo pattern frequency employed to position the magnetic head in a radial direction based on a radial position of the magnetic head.

A storage device includes read circuitry having a read head having a detector that outputs signals representing data from a first track and an adjacent track. The read head is subject to off-track excursions during which the read head detects signals from both the first track and an adjacent track. Data on each track includes a preamble including a repeating pattern. The repeating pattern in any first track is orthogonal to the repeating pattern in any track adjacent to the first track. The read circuitry also includes respective Discrete Fourier Transform circuits to identify components in the signals corresponding to respective frequencies characteristic of the repeating pattern on the first track and the repeating pattern on the second track, and computation circuitry to determine from the components a ratio by which the read head is off-track. Corresponding methods are provided for operating such a storage device and for reading data.

A diagnostic tape (318) for use with a tape drive (310) having a tape head (322) includes a first tape section (430A) and a second tape section (430B). The first tape section (430A) and the second tape section (430B) are configured to move across the tape head (322) during use of the tape drive (310). The first tape section (430A) includes a first patterned data code (432A) that is indicative of a first spacing between the tape head (322) and the first tape section (430A). The second tape section (430B) includes a second patterned data code (432B) that is indicative of a second spacing between the tape head (322) and the second tape section (430B). The second patterned data code (432B) is different than the first patterned data code (432A). The diagnostic tape (318) can further include a tape head cleaning section (630F) including abrasive material (650) that is configured to move across the tape head (322) to clean the tape head (322).

A data storage device is disclosed comprising a head actuated over a disk surface comprising a first magnetic recording layer and a second magnetic recording layer. Data is encoded into a codeword comprising a plurality of non-binary symbols wherein each symbol represents one of a plurality of symbol values comprising a first symbol value, a second symbol value, and a third symbol value. The first symbol value is written to the disk surface by magnetizing the first and second magnetic recording layers, and the second symbol value is written to the disk surface by magnetizing the first magnetic recording layer without substantially affecting the magnetization of the second magnetic recording layer. The encoding into the codeword codes out at least one sequence of symbol values to prevent an ambiguity between detecting the first symbol value and the second symbol value during a read operation.

Disclosed herein are a system, non-transitory computer-readable medium, and method for encoding and decoding information on a data bearing medium. A message comprising a bit string is read. A plurality of substrings in the message may be associated with a phase invariant codeword.

There is provided a disk-type recording medium, a recording apparatus, a recording method, a reproducing apparatus, and a reproducing method, which are capable of recording, for example, data with high density and reproducing data recorded with high density robustly. In the disk-type recording medium, synchronization patterns for synchronization are recorded in two adjacent tracks with a shift in a track direction so that positions in the track direction do not overlap. The present technology can be applied to, for example, optical discs, other disk-type recording mediums, and the like.

A storage device includes read circuitry having a read head having a detector that outputs signals representing data from a first track and an adjacent track. The read head is subject to off-track excursions during which the read head detects signals from both the first track and an adjacent track. Data on each track includes a preamble including a repeating pattern. The repeating pattern in any first track is orthogonal to the repeating pattern in any track adjacent to the first track. The read circuitry also includes respective Discrete Fourier Transform circuits to identify components in the signals corresponding to respective frequencies characteristic of the repeating pattern on the first track and the repeating pattern on the second track, and computation circuitry to determine from the components a ratio by which the read head is off-track. Corresponding methods are provided for operating such a storage device and for reading data.

According to one embodiment, a magnetic recording and reproducing device includes an output driver, a magnetic head, and a magnetic recording medium. The output driver outputs a recording signal corresponding to input information. The magnetic head includes a coil. A recording current includes the recording signal flows in the coil. Information corresponding to the input information is recorded in the magnetic recording medium. The input information includes first, second, and third information combinations. The first information combination includes first to fourth information. The second information combination includes fifth to eighth information. The third information combination includes ninth to twelfth information. The recording signal changes to an eleventh recording current to correspond to the eleventh information. The recording signal changes to a third recording current to correspond to the third information. An absolute value of the eleventh recording current is greater than an absolute value of the third recording current.

Disclosed are systems, methods, and devices for increasing the storage areal density of a storage device. In one embodiment, a method is disclosed comprising receiving host data, the host data including first data and extra bit data; generating run-length limited (RLL) data by encoding the first data with an RLL encoder; generating a symbol corresponding to at least one bit of the extra bit data; and generating superpositioned data by inserting the symbol within a contiguous section of repeating bits in the RLL-encoded first data.