Abstract: A pipelined Viterbi decoder includes a plurality of circuit stages and a synchronous clocking arrangement for controlling the operations of the circuits within each stage. Specifically, an input stage converts multi-level input signals into streams of even and odd digital data samples. A parallel-precomputation stage adaptively establishes a threshold range for each sample, while a sequence detection stage designates one of the multiple levels for that sample and then determines the validity of that designation. Validity is determined in accordance with the sequence property of alternate samples in multi-level coding. Violations of the sequence property are corrected by a sequence correction stage so that valid, coded data and clock signals are provided at the outputs of the decoder.

Abstract: A magnetic transducer for reproducing/recording high frequency signals with a magnetic tape medium includes a pair of opposed transducer head halves separated by an insulation gap and bonded together to form a Y-shaped pole structure, each half including a laminated at least partially ferromagnetic core portion bounded on opposite surfaces with outer and inner conductive layers, each of which forms a winding coil portion. Each core section has a leg portion and an angularly disposed arm portion, the distal end of which is capped with a block-shaped ferromagnetic pole tip in magnetic path relation therewith, the two pole tips lying in a common plane transverse to the plane of the gap. The conductive layers, when conductively interconnected, such as by jumpers, form a one or two turn coil for the transducer.

Abstract: A tubular member defining a shield is formed of a pliable yet resilient plastic split along one side of its length. The cross section of at least one end is selectively tapered to provide an extended end portion at the extreme end of the tapered cross section. The extended end portion facilitates the pressing of the split tubular member onto a selected length of a graphite shaft of a golf club, to prevent wear on the graphite shaft by the divider sections of a golf bag when the clubs are being carried in the bag.

Abstract: Input data symbols are written to a synchronization (sync) adder, which appends a pseudo randomly (PN) generated sync bit to generate a sync word. Sync words are sent to a receiver where synchronization is recovered. The receiver re-generates the same PN sequence that was generated at the transmitter. Synchronization recovery apparatus conceptually looks at each bit position to locate the appended PN sequence. When the sync bit position is found, the data stream is assembled into fixed length sync words and the data symbols of the sync words are written into a buffer at an address determined by the position of the sync bit in the PN sequence. Error rates in the data stream of sync words are measurable using a correlator network for reading the bit in the sync bit position of a sync word and for comparing that bit with its expected value in a reconstructed PN sequence to provide a difference value where the difference is a measure of the error rate in the data stream.

Abstract: A method and apparatus for the generation of a signal flag in response to illegal channel code patterns from an information channel, the signal flag may typically be used as an erasure flag by a subsequent error correction decoder. This erasure flag, being indicative of a data error position which can then be fed into a utilization circuit such as an error correction logic for performance improvement. In particular, a Miller-squared channel code format decoder in accordance with the present invention can easily and inexpensively provide error position information thereby enhancing error correction power, such as that of a Reed-Solomon error correction code.

Abstract: Input data symbols are written in a write buffer then to a sync adder, which appends a pseudo randomly (PN) generated sync bit to the MSB position of a four-symbol sync word data field, to generate a sync word. Sync words may or may not be randomized and sent to a receiver whereafter synchronization is recovered and perhaps de-randomized symbols are written into particular positions of an ECC block in a read buffer which are derivable from the PN sequence. The ECC block is a data array having multi-bit sync words making up its rows and the bit positions of the sync words making up its columns. Synchronization recovery apparatus conceptually looks at each bit position across a row and in a top-to-bottom direction down each of the columns to locate that column which contains the appended PN sequence. Sync recovery involves the receiver re-generating the same PN sequence that was generated at the transmitter.

Abstract: In a data compression process such as employed to compress video or other data, it is preferable not to compress the image data representative of the video image in a sequential format, or to take the data from the same area of the image. To equalize the information content of the data prior to compression, the present shuffling/deshuffling technique divides the video image into a multitude of image representing blocks, and selects a predetermined number of the image blocks from different spatial locations in the image, to form a succession of data sets representative of the video image information. That is, the selection of the image representing blocks is such that the information content (complexity) in each data set is similar to the information content in each other data set and further similar to the average information content of the entire video image.

Abstract: A feedforward circuit applies a capstan drive current, or its equivalent, to the reel tension servo circuits whose associated reels are transporting the tape. The additional drive current to the reel drive motors increases the rotational velocity of the reels to maintain the same resultant acceleration between the tape driven by the capstan and the tape being transported between reels. Since the tape pack affects the gain of the feedforward circuit, a preselected average gain corresponding to the mean tape pack diameter is used to match different cassette sizes. A microprocessor may be used to provide the various signals and may vary the gain of the feedforward circuit not only in response to reel size but also in response to instantaneous reel tape pack diameter.

Abstract: Error concealment of an erroneous pixel in a line of pixels is provided by adaptively using a large number of adjacent correct pixels along the same horizontal line. The invention discards any corrupted adjacent pixel which would be used in the calculation for a replacement pixel value, while modifying the weighting of the remaining adjacent correct pixels in accordance with the error pattern generated by the corrupted pixel or pixels. An overflow detection circuit also is included, which provides an acceptable replacement pixel value rather than using the unacceptable overflow value.

Abstract: An improved head mounting assembly includes a wedge-shaped rigid head support member which minimizes resonances when operating at rapid transverse head movements, and which operates in conjunction with a photo-sensitive head positioning apparatus, to provide improved tracking for a transducing head mounted on the member.

Abstract: An image data compression technique is described which utilizes calculating means and a selected series of bit calculating stages having delays, to estimate one or more quantization parameters for such data. The estimation process preferably is iterated a number of times, with the values found through each estimation being used as the trial values for subsequent estimations. In addition, an initial trial value is selected by a data look ahead technique, which assures that its value is within range of the final quantization parameter used to quantize the data. The final quantization parameter insures that the compressed data fits within a predetermined number of encoded data bits to be transmitted or recorded, for example, in a recording medium.

Abstract: A slave device detecting system utilizes the past history of devices connected to a data bus to optimize the time required to re-establish communications. Whenever a master controller senses a condition that requires an assessment of devices on the bus, it examines the addresses of previously connected devices at more frequent time intervals than it does for addresses that were not previously associated with connected devices. In a preferred approach, all valid addresses can be examined in a sequential fashion, and the address of the previously connected device can be examined at every fifth or tenth position in the sequence. With such a technique, a device will be detected much faster once it has returned to the bus.

Abstract: A scan tracking centering algorithm is not left at a nominal value, but is modified based on a tape timer's position into the field. That is, the scan tracking centering is adjusted forward (i.e., down) if the tape timer indicates the tape position is early in the field, and is adjusted back (i.e., up) if the indicated tape position is late in the field. Thus, the head deflection control decision which determines if the jumps, or doesn't jump, is made dependent upon tape position in the field, as well as on head elevation.

Abstract: The decision feedback decoder of the invention receives sequentially sampled values of a signal waveform corresponding to data bits transmitted by a channel. A magnitude comparator compares the sampled values to a threshold and based on each comparison it provides subsequent decisions determining the values of the corresponding data bits. A predetermined number of previous decisions are stored and applied to a first and a second threshold adjustment circuit. Each circuit adjusts the threshold depending on the respective values of the previous decisions, while the first circuit provides the adjustment based on an assumption that the next decision to be made will have a first signal value and the second circuit provides the adjustment based on an assumption that the next decision will have a second signal value. When that next decision becomes available, it is utilized to select the correct adjusted threshold value for the next comparison by the magnitude comparator.

Abstract: In a head displacement measuring apparatus, a folded optical path is used to introduce a collimated beam of light from a light source to a split photo detector, wherein both the light source and the split photo detector are mounted external of the support housing which secures and supports the flexible head assembly. A pair of optical prisms direct the light beam parallel to a head supporting blade integral with the head assembly. A Fresnel lens secured to the blade, preferably at the head end, varies the position of the path of the light beam in response to lateral displacement of the blade and head, to likewise vary the extent that the beam impinges one or the other of the photo detectors. The difference of the signals from the split photo detector provides a precise measurement of the transverse displacement of the head from a nominal centered position.

Abstract: A record current optimization technique includes a magnetic reference tape pre-recorded with a selected frequency at a precisely known level into the tape. A magnetic tape recorder is loaded with the reference tape, and a reference playback level is recovered from the reference tape with a playback head, and is stored or otherwise noted. A recording at the selected frequency then is made with a record head on an unrecorded portion of the reference tape. The new recording is simultaneously read out with the playback head and record current automatically or manually is adjusted until the new playback level matches the reference playback level. A value corresponding to this optimized record current is stored. The record head thus is optimized for any subsequent recording process, by selecting the stored value corresponding to this value. The optimization technique may be employed to optimize record currents in audio, video and data, analog or digital, recorders.

Abstract: Structures of magnetic heads having superconducting shields are disclosed for spatially directing magnetic recording/playback fields. One embodiment is a thin film magnetic head with a layer of superconductor material associated with its throat. Further embodiments provide intertrack shielding and concentration of recording/playback fields into relatively small pole tip regions.

Abstract: To produce a simulated airbrush spray pattern comprising a random pattern of pixels in a video image, multiple source arrays defining random variations of one or more video image parameters are created. Each time that an airbrush spray pattern is to be generated on a video display, the source arrays are individually retrieved and used to control the characteristics of corresponding pixels in the video image. The arrays are varied on a regular basis to create a random pattern in the image that simulates the effects of an airbrush spray. Various modifications can be used to create particular effects and position dependent textures, such as the short, random streaks that are produced by chalk.

Abstract: A pantographic head mount includes a pair of generally parallel flexible arms each solidly based at an inboard end and solidly affixed at an outboard end to a rigid structure that carries a magnetic head and is driven by an electromagnetic motor positioned to hold the head continuously normal to a recording medium while traversing across the medium. The structure is particularly adapted to resist torsional deformation. The two arms may be structured to have different resonant frequencies, and beating resonance between the arms during high-speed operation is avoided. However, in such case, the structures of the two arms are carefully matched to ensure that they still maintain the head continuously normal to the recording medium. In another embodiment, the arms have differently reticulated structural configurations to present incongruent but equal-area cross-sections at various points along the arm lengths.

Abstract: A multi-channel rotary optical coupler incorporates a multi-element lens assembly formed of a coplanar plurality of annular convex lens elements, with each lens element of the assembly having a substantially constant annular width and a discrete optical axis, with each optical axis of each lens element radially displaced about a central rotational axis of the coupler. Each lens element receives an output from a respective data modulated light source and provides discrete data channels for the continuous transmission of discrete data signals through the lens elements to respective similarly radially displaced optical detectors of a detector array.