Abstract: Multiple symbol correction employing auxiliary pointers is enhanced by unique interaction of code structures either with ambiguous auxiliary pointers or data structures for precisely locating errors. For example, a code apparatus can correct two symbols in error only with two error location pointers; with three error location pointers, the code cannot correct the errors since error location is ambiguous. Once this has been determined, the features set forth in the present invention are employed to delimit the error burst such that the code apparatus may correct two symbols in error, even with ambiguous error location pointers. With no auxiliary pointers, methods and apparatus can create such auxiliary pointers in particular data structures and error patterns.

Abstract: Within a cleaning station for an electrostatic copier, a rotatable scavanging roll has a peripheral scavanging surface. Particulate matter, including toner entrained in an air stream, passes by the scavanger roll; the roll being electrically charged attracts a portion of the entrained particulate material. An air permeable filter is in cleaning contact with one circumferential portion of the scavanger roll for at least partially cleaning particulate matter therefrom, while simultaneously capturing entrained particulate material not attracted to the scavanging roll. In a preferred form, the cleansing filter has a relatively coarse mesh adjacent and contacting the scavanging roll and at an air-receiving portion. The filter has an exit portion of relatively fine mesh for capturing all particulate material.

Abstract: Data signals are linearly recorded on a record medium as a sequence of discrete amplitude levels, each level occurring in a bit period. For each received data bit signal, a separate sequence of such levels is generated in accordance with a predetermined rule such that each separate sequence of levels extends over a predetermined number of data bit periods. All of the amplitude levels from a plurality of data bit signals occurring in each data bit period are summed together to provide a resultant amplitude to be recorded. Such resultant amplitude in each data bit period is linearly recorded on the record medium. Readback and detection of such recorded signals is accomplished by first recovering data bit signals by supplying the readback signals through a filter matched to the sequence (preferably a tapped delay line) for reconstituting the data bit signals. The reconstituted data bit signals are then detected using known data bit detection techniques.

Abstract: An improved magnetic tape test article includes a plurality of longitudinally spaced-apart test sections. Some of the test sections are repeated to facilitate recorder tests under different tape wrap conditions. One of the tests is a compound test enabling several simultaneous measurements of several parameters of the recorder. The tests are particularly adaptable for helical scan digital signal recorders. The tests measure parameters such as head to medium spacing, tracking (skew, servo offset and the like), readback circuit performance, including clocking, phase tolerances, error detection and correction operations, response to dropouts, resynchronization response and amplitude tolerances. Profile of the spacing between the record medium and the head is measured over the length of the recorded path around the cylindrical mandrel.

Abstract: A signal storage apparatus employs a stack of circular record disks accessible by axially separating segments of selected disks in the stack. One disk in a stack of coaxial rotatable circular compliant record disks is accessed with a minimum energy imparted to such disks by a chord roll disk separator. In a preferred form, the chord roll disk separator induces a primary bending mode to some of the disks being axially separated. In another aspect of the disclosure, a signal transducer is mounted integrally with the disk separator. With such mounting, primary, secondary, or higher order bending modes may be successfully employed. Full chordal and partial chordal axial disk separations are described. Arcuate and radially directed separation techniques may be employed. A unique axial stacking arrangement for compliant record disks is also described.

Abstract: An elongated magnetic tape has a pair of longitudinally extending servo track areas, one of which is closer to the longitudinal center of the tape than the other. The lateral space intermediate the servo areas receives data signals, while the space between said one servo area and one edge contains identification and address signals. The tape is particularly adapted for use with rotating head recorders having two gaps on the rotor, with an intergap distance slightly greater than the lateral extent of the servo areas. A recording or write gap precedes an immediately trailing reading or recovery gap. When the rotor gaps pass the one edge in the one servo area, the write gap senses the servo track; while the read gap senses the identification signals. The arrangement is such that prior to the time the write gap reaches the data recording area, the read gap has sensed the identification signals.

Abstract: A track or stripe tape positioner for a helical scan or rotary head recorder uses digital techniques. The expected step size is preset into a counter. During the next phase, a calibration phase, the tape is stepped through a plurality of stripes whereat the preset value is adjusted to measured values. In the third phase, the average step size is maintained subject to certain averaged changes thus providing a high degree of noise rejection to ensure reliable incremental stepping of a record tape through the recorder.