Abstract: Method and apparatus are provided for developing a digital timing signal indicative of when a head of a helical scan recorder (30) is positioned over a recorded stripe on magnetic tape (32). The method involves rotating a drum (36) upon which a head is mounted while the magnetic tape (32) is transported past the drum at a speed greater than the nominal speed at which stripes were recorded on the tape. Given the geometry of the system and format of the tape, the head is eventually able to recognize a pattern of digital data. The timing of the recognition of the pattern of digital data is used to determine the precise time, relative to each rotation of the drum (36), that the head ceases to traverse a stripe and the precise time during each rotation of the drum that the head begins to traverse a stripe. The determination of the edges of the digital timing signal is repeated upon every rotation of the drum (36).

Abstract: A helical drive system (10) reads tracks (18) on a storage medium (12), including tracks which appear as distorted tracks. Each track (18) comprises a plurality of blocks of data, with each block having unique block-identifying information. A track-following servo system (84) causes a read head (16C) to traverse predetermined original azimuthal paths (P0) across the storage medium (12) for reading the blocks recorded along each of the original azimuthal paths (P0). A controller (50) uses the block-identifying information to determine whether any blocks expected to be read during the traversal of the original azimuthal paths (P0) were not read. If expected blocks were not read, the controller (50) repositions the storage medium (12) and directs that the medium (12) be re-read with the head (16C) positionally offset until the expected blocks are actually read. During the re-read attempts, the read head (16C) is positionally offset to traverse sets of modified azimuthal paths (P1, P2, P3, . . . P10 ).

Abstract: Apparatus and method are disclosed for enabling rapid search of magnetic tape having information helically recorded thereon. A tape mark, consisting of an analog signal, is recorded on the magnetic tape as a physical location reference in a manner such that the mark can be detected at both normal playback speed and at faster search speeds. The recorded analog signal provides a highly reliable indication of record boundaries, including end of file, end of volume, end of directory, and the like.

Abstract: A tracking system and method are disclosed for a helical-scan recording device to automatically maintain the recording/playback heads in alignment with the stripes of recorded information on the magnetic tape. Each stripe on the magnetic tape includes a servo area having four distinct zones. An analog servo signal at a preselected frequency is recorded on one of the four zones on each stripe and is recorded at different ones of the four zones in succession on each group of four adjacent stripes. The servo signal recorded on the stripes is detected during playback and processed to maintain the desired head positioning relative to the stripes on the tape. The servo head is preferably maintained between adjacent stripes on the magnetic tape and signals detected from each of the adjacent stripes maintain head alignment by shifting the positioning of the head in either direction as needed.

Abstract: A system and method of adaptively modifying the control signal of a servo system during a mode of acceleration or deceleration. An error accumulator, mean generator, and feedforward generator are used to generate a feedforward signal which modifies the control signal delivered to the servo motor. The feedforward signal for a given mode of operation is determined by the mean error during the previous operation in the mode and by the feedforward signal used during the previous operation in the same mode. Each subsequent operation in the same mode improves the feedforward signal until the mean error is minimized.

Abstract: A method and system for detecting tape attachment to a machine reel of an automatically threading magnetic tape system. During the threading process, a file reel is rotated to allow a sufficient length of tape to be unwound therefrom, which length of tape eventually attaches to the machine reel after being automatically threaded through the desired tape path. The rotation of the file reel is maintained during this threading process by delivering current pulses to a file reel motor. These current pulses are counted per unit time. As soon as the tape attaches to the machine reel, the machine reel begins to pull the tape from the file reel, thereby eliminating the need to deliver current pulses to the file reel motor, at the same rate as needed prior to tape attachment. A change in the rate of the current pulses delivered to the file reel motor signals a tape attached condition.