Abstract: The invention provides a channel coding method for encoding systematic data for transmission in a communication channel. The systematic data has a runlength constraint. In the method, data words are permuted. Error codes are generated based upon the permuted data words. The error codes are appended to original data words to form channel input for serial transmission in the communication channel. The number of error code bits is limited to ensure the channel input meets the runlength constraint. The error code can be a parity check bit.

Abstract: A method uses an outer code that is a concatenation of code words generated by a parity check encoder. The outer code word is permuted by an interleaver. The high rate coding provides good performance with a simple structure. A parity check bit is generated for each data word of received systematic dates. Code words are formed by adding a generated parity bit to each data word. Groups of code words are permuted to form encoded input for transmission in a communication channel. The invention further includes encoding to maintain a runlength-limiting (RLL) constraint at the channel input. Interleaved runlength encoded system data is used to generate error code bits. Insertion of error code bits in the system data at the channel input is controlled. This guarantees that the channel input stream comprised of the runlength-limited system data and inserted error code bits meets the runlength constraints.

Abstract: A method uses an outer code that is a concatenation of code words generated by a parity check encoder. The outer code word is permuted by an interleaver. The high rate coding provides good performance with a simple structure. An odd parity check bit is generated for each data word of received systematic dates. Code words are formed by adding a generated parity bit to each data word. Groups of code words are permuted to form encoded input for transmission in a communication channel. The invention further includes encoding to maintain a runlength-limiting (RLL) constraint at the channel input. Interleaved runlength encoded system data is used to generate error code bits. Insertion of error code bits in the system data at the channel input is controlled. This guarantees that the channel input stream comprised of the runlength-limited system data and inserted error code bits meets the runlength constraints.

Abstract: A method uses an outer code that is a concatenation of code words generated by a parity check encoder. The outer code word is permuted by an interleaver. The high rate coding provides good performance with a simple structure. An odd parity check bit is generated for each data word of received systematic dates. Code words are formed by adding a generated parity bit to each data word. Groups of code words are permuted to form encoded input for transmission in a communication channel. The invention further includes encoding to maintain a runlength-limiting (RLL) constraint at the channel input. Interleaved runlength encoded system data is used to generate error code bits. Insertion of error code bits in the system data at the channel input is controlled. This guarantees that the channel input stream comprised of the runlength-limited system data and inserted error code bits meets the runlength constraints.

Abstract: A method and means for detecting spectral null sequences of a spectrally-constrained code at the output of a noisy communications channel by tracking the spectral content of said sequences with a Viterbi detector using an N stage trellis and mapping each spectral null sequence to a unique path of acyclic successive states and edges through said trellis by selectively outsplitting counterpart states at preselected times modulo N in said trellis such that no pair of unique paths support the same spectral null sequence.

Abstract: Apparatus and method for transmitting spectral null sequences of a spectrally-constrained code over a partial response channel. A Viterbi detector receives the sequences from the channel and has a time-varying detector trellis structure derived from a running-digital-sum (RDS) trellis structure that requires each one of a set of quasicatastrophic sequences to be generated only from a trellis state corresponding to a respective preselected unique RDS value.

Abstract: A modulator apparatus for modulating arrays of input data V.sub.in to be stored in a holographic recording medium is disclosed wherein the final output data array V.sub.out has frequent transitions from light to dark and from dark to light in either dimension across the data page and has the total amount of illuminated regions throughout the entire data page held constant. These two constraints are achieved by a first set of control arrays obtained from two fixed sets of m.times.n binary arrays {A.sub.0, A.sub.1, . . . , A.sub.n } and {B.sub.0, B.sub.1, . . . , B.sub.m } which in turn are obtained from fixed sets of binary control vectors {a.sub.0, a.sub.0, a.sub.1, . . . , a.sub.n }, {b.sub.0, b.sub.1, . . . , b.sub.m }, respectively. The control vectors a.sub.0, a.sub.1, . . . , a.sub.n any n+1 fixed elements of the inverse mapping, .phi. .sup.1 (C.sub.1), of the (t-2) error-correcting code C.sub.1 of length m. The control vectors b.sub.0, b.sub.1, . . . , b.sub.

Abstract: Maximum likelihood detection of a trellis code using a Viterbi detector constructed from a time-varying trellis structure that is associated with a partial response channel and consists of connected trellises with periodically repeated patterns of nodes and subtrellises of said trellises. Each subtrellis has nodes representing a current state of the channel and value of a predetermined tracked attribute. A survivor metric and a survivor sequence from a node at the end of one subtrellis are reassigned to a node at the beginning of an adjacent subtrellis having a different value of the tracked attribute for increasing minimum distance properties, reducing error event length and improving code constraints for timing and gain control. The one subtrellis and adjacent subtrellis may be within a single trellis or in adjacent trellises.

Abstract: A breakaway unit which is adapted to be mounted in series flow relation with a fuel nozzle. The breakaway unit comprises a flex section which assures an axial transmission of forces to a valve section which is separated when a vehicle drives away from a dispensing unit with the nozzle lodged in its fuel tank. The valve section comprises inlet and outlet couplers and means for releasable locking the couplers in an assembled relation. These means comprise fingers which are flexed outwardly when a separating force exceeds a predetermined value. Garter springs embrace the fingers to accurately control at which the couplers will separate. The fingers engage angularly spaced lugs which permit the fingers to be telescoped therebetween and then rotated to a locking position to facilitate reassembly of the couplers with a minimum of effort. Alternate embodiments of the invention disclose other forms of spring means for accurately controlling the force at which the couplers will separate.

Abstract: An encoding apparatus for constructing an asymptotically optimal coding scheme for second order DC-constrained channels is disclosed. A first encoding function block breaks an input data stream into equal sized vectors of length m bits. A sign designation bit is then attached to each vector to make vectors of length m+1 bits. r redundancy bits are added to each vector, to produce balanced vectors of length m+1+r bits. A first moment is calculated for each vector. A determination is made whether the addition of this vector's first moment value to an accumulated running sum of all the vectors' first moments effectively drives the running sum in the direction of zero. If is does then that vector's first moment is added to the accumulated running sum of first moments and the vector is added to the output array.

Abstract: A Viterbi decoder having a recursive processor modified to process each node in a trellis of a partial response coded signal to shift the branch metric additions over the node to effectuate compare, select, add operation order on the predecessor survivor metrics terminating in that node, to compare the metrics of the predecessor sequences terminating in the node, to select a survivor sequence, and to add the shifted branch metrics to the metric of the selected survivor sequence.

Abstract: A method and apparatus for detecting spectral null sequences of a spectrally-constrained code on a noisy communications channel. From a Viterbi detector with a trellis structure comprising a plurality of states and edges, predetermined ones of the states and edges in the trellis structure are deleted at preselected times modulo N, such as times .phi. modulo N and/or at intermediate times m modulo N, where m=.phi., thereby to create a time-varying trellis structure for limiting the maximum length of dominant error events. The deleted edges are generally those edges which would have entered or emanated from the deleted states if they were not deleted. The trellis structure may be a so-called systolic structure, in which case the spectral null sequences are preferably DC-free or Nyquist free.

Abstract: A breakaway unit which is adapted to be mounted in series flow relation with a fuel nozzle. The breakaway unit comprises a flex section which assures an axial transmission of forces to a valve section which is separated when a vehicle drives away from a dispensing unit with the nozzle lodged in its fuel tank. The valve section comprises inlet and outlet couplers and means for releasable locking the couplers in an assembled relation. These means comprise fingers which are flexed outwardly when a separating force exceeds a predetermined value. Garter springs embrace the fingers to accurately control at which the couplers will separate. The fingers engage angularly spaced lugs which permit the fingers to be telescoped therebetween and then rotated to a locking position to facilitate reassembly of the couplers with a minimum of effort. Alternate embodiments of the invention disclose other forms of spring means for accurately controlling the force at which the couplers will separate.

Abstract: A breakaway unit which is adapted to be mounted in series flow relation with a fuel nozzle. The breakaway unit comprises a flex section which assures an axial transmission of forces to a valve section which is separated when a vehicle drives away from a dispensing unit with the nozzle lodged in its fuel tank. The valve section comprises inlet and outlet couplers and means for releasable locking the couplers in an assembled relation. These means comprise fingers which are flexed outwardly when a separating force exceeds a predetermined value. Garter springs embrace the fingers to accurately control at which the couplers will separate. The fingers engage angularly spaced lugs which permit the fingers to be telescoped therebetween and then rotated to a locking position to facilitate reassembly of the couplers with a minimum of effort. Alternate embodiments of the invention disclose other forms of spring means for accurately controlling the force at which the couplers will separate.

Abstract: A method for coding a binary data string for a partial-response channel having a transfer function with a spectral null at zero frequency to provide a coding rate 8/10 and an output which is invariant to 180-degree phase shifts in the channel output signal. A finite-state machine is created having two pairs of states and a plurality of codewords each corresponding to a respective binary data byte. The binary data string is encoded by said machine into a string of binary codewords having a power spectrum value of zero for a frequency of zero. In response to each successive data byte in the binary data string, there is generated one of two complementary codewords from the one of that pair of the states designated by said machine as corresponding to the data byte for the then current state of the machine.

Abstract: This disclosure concerns for generating asymmetrically constrained run-length-limited encoded data from a serialized binary string of 1's and 0's. The method comprises the steps of encoding the input data bits using a run-length-limited constraint in the form of M/N (d,k), where M is the number of input data bits, N is the number of output bits associated therewith, d is the minimum number of 0 data bits between adjacent data bit 1's, and k is the maximum number of 0 data bits between adjacent 1's; and alternating the values of d and k between a set (d.sub.1, k.sub.1) and a set (d.sub.2, k.sub.2), respectively, where d.sub.1 .noteq.d.sub.2. The apparatus comprises means for generating N output data bits in response to M input data bits and for generating data bit 0's between data bit 1's based upon a run-length-limited coding constraints (d.sub.1, k.sub.1) and (d.sub.2, k.sub.2), where constraints (d.sub.1, k.sub.1) and (d.sub.2, k.sub.2) apply alternately to runs of zeroes between output data ones.

Abstract: An improved method is described for coding input strings to improve reliability of partial response channels. This method comprises encoding an input string into an intermediate string using a binary convolutional code, and encoding the intermediate string using a nonlinear inner code that repeats and inverts selected bits of the intermediate string. The inner code has a coding rate of less than one. As specifically illustrated, this method provides coding gains for partial response channels of at least 4.8 dB.

Abstract: A method is disclosed for coding input strings for a partial response channel to provide an output having a reliability determined by a preselectable coding gain. This method involves determining each frequency at which there is a zero in the transfer function of the partial response channel, and then encoding an input string into a binary code string having a power spectrum value of zero for each such frequency. A channel output sequence is generated responsively to transmission of the code string through the channel. The most probable sequence among those having a power spectrum value of zero is then calculated from the channel output sequence and decoded to provide the output.

Abstract: Uncompressed data is represented in a constrained code for transmission through a channel which may include record media. A d,k code having a code rate of m/n is employed. "d" represents the minimum number of successive zeros in the channel code while k represents the maximum number of zeros in the channel code. "n" is an integer representing the number of code bits in a channel group. The encoding and decoding follows a sliding block coding and decoding algorithm. In the channel coding, the number of successive ones is limited to being not less than two, in some coding it can be a value of d-1. The modification of the d,k code results in decreasing error propagation while increasing the recorded information density. This increase is achieved by increasing the channel code dictionary.

Abstract: Encoding method for data to be recorded on optical disks using the pit-per-transition technique or return-to-zero techniques whereby the characteristics of the encoded bits produce a stable, low frequency spectral notch and minimum interference with associated focus and tracking servomechanisms. RLL (d,k) code words are selected so that the ratio of the lengths of pits and lands approximate some nonzero fraction less than one-half which depends on the (d,k) code employed. For example, a fraction of 1/3 is appropriate for RLL (2,7).