Abstract: A carrier sense multiple access with collision detection strategy ascertains for a particular network configuration the network propagation time, and promulgates a parameter p providing an indication thereof to each station of the network. Each station of the network stores p for use in making decisions about collisions. Whenever a modification of the network is made changing the propagation time, a new value of p is promulgated to the stations of the network so that the collision related decisions made by each stations's interface controller will reflect the new network configuration. Communications are formed in packets with a preamble long enough to propagate the network. The controllers analyze the signals they receive to discern whether a packet has been contaminated by an interference.

Abstract: A differential detector is disclosed that is used in FM or PM receivers for demodulating a modulated carrier signal. The detector uses a mixer/phase detector for combining an intermediate frequency phase modulated or frequency modulated signal with the same signal delayed to demodulate the signal. Delay inherrent in an IF filter of the receiver in which the detector is utilized for this purpose. The undelayed and delayed signals required for operation of my differential detector are obtained from the input and output respectively of the IF filter. The output from my detector has spurious signals not typically present in the output of prior art differential detectors but these spurious signals are removed by a filter including low pass, band reject and/or notch filtering to yield only the modulating signal.

Abstract: A pattern recognition system has both coarse and fine levels of analysis in which a coarse array representation of a workpiece pattern is formed and used to identify the workpiece pattern as either a referench character or as a member of an ambiguous set of reference characters which are represented by identical coarse array representations. At least portions of a fine array representation of a workpiece pattern which has been classified as a member of a set of reference characters are compared to corresponding portions of fine array representations of reference characters in the set identified by the classification. The pattern recognition system has a learning system through which reference characters may be introduced into the recognition system and through which a representation of a workpiece pattern which was not identified may be incorporated into an existing set of reference characters of the recognition system.

Abstract: A broadband data communication system provides effective increased bandwidth for the transmission of electrical information signals in the system. The signal transmission medium is a coaxial cable having main receive and transmit branches, and having drop line pairs connected to the main branches at junction points. A plurality of user devices is connected to each drop line pair, including a particular set connected to a particular pair. Each user device of the set can transmit and receive signals of local frequencies in a selected bandwidth. Frequency isolation means is connected to the particular drop line pair adjacent its junction point, and passes signals of the local frequencies only from the transmit drop line to the receive drop line, while blocking signals of the local frequencies from transmission over the main cable branches. The particular set of user devices and the filter isolation means together define a subnet.

Abstract: Apparatus is disclosed which functions with a scanning arrangement including a charge coupled device (CCD) scanner and an analog-to-digital converter to digitize documents for storage, display and transmission to a remote location. The apparatus is attached to the scanner and consists of a reticle with a site pattern thereon, a lens arrangement and a lamp which are used to position a document for scanning. Prior to scanning the document the lamp is briefly energized to project the pattern onto an easel on which the document is placed, and the portion of the document on which the pattern is projected is the portion that will subsequently be scanned by the scanner.

Abstract: A high density dot matrix printer is disclosed which can print characters with variable font and having print resolution close to that of a typewriter. Printing on both a forward and reverse pass of a line of characters with the dot print head coupled with offsetting the dot matrix print head for the reverse pass printing doubles the line density in printing characters to increase resolution. In addition, a compacted character code arrangement is utilized having a different printing code for the reverse pass printing than for the forward pass printing, and uses single binary words to represent many dot printing positions dependent on the location of the single binary word in the character code coupled with using single binary words to represent many possible dot positions in which no dots are to be printed.

Abstract: A communication network (10) has a memory unit (20) accessable to all ports (16-0, 16-1, 16-2, 16-3) of the link with a plurality of local sections (62) each associated with one of the ports. Interconnections include a dual memory bus (28) with a common bus subsystem (36) providing access to a common memory section and a local bus subsystem (30) providing access to the local memory sections, the subsystems constructed to permit concurrent independent use. Memory access priority circuitry (68) designates for each memory operating cycle a port for current service and makes memory access available to other elements when not required by the designated port.

Abstract: For use in data processing systems, an improved controller to control a plurality of peripheral data storage means having different characteristic data transfer rates. The controller has a similar plurality of instruction storage units, a single instruction register, and common operating circuitry for the data storage means. The controller responds to data transfer commands from the system central processor to select an instruction storage unit, and to the characteristic data transfer rate of a selected data storage means sequentially to address instructions within it, at a rate corresponding with the characteristic data transfer rate. The addressed instructions are sequentially output to the instruction register; the common operating circuitry is responsive to the outputs of the instruction register to transfer data as commanded by the central processor.

Abstract: A data processing machine in which the cache operating cycle is divided into two subcycles dedicated to mutually exclusive operations. The first subcycle is dedicated to receiving a central processor memory read request, with its address. The second subcycle is dedicated to every other kind of cache operation, in particular either (a) receiving an address from a peripheral processor for checking the cache contents after a peripheral processor write to main memory, or (b) writing anything to the cache, including an invalid bit after a cache check match condition, or data after either a cache miss or a central processor write to main memory. The central processor can continue uninteruptedly to read the cache on successive central processor microinstruction cycles, regardless of the fact that the cache contents are being "simultaneously" checked, invalidated or updated after central processor writes.

Abstract: There is provided improvements in magnetic recording head arrangements, such as may employ multiplexing, which provide substantially higher speeds of recording and require fewer components. The recording head is comprised of a compact, four-layer laminate structure mountable on a supporting substrate, in which the entire array of recording elements forms a flexible, uniquely arranged first layer, the return paths of the recording elements comprise a flexible second layer which has the dual utility of substantially reducing the recording element circuit inductance, the third layer is a rigid printed circuit board structure providing a mount for the blocking diodes and the conductive paths of the associated multiplexing scheme, and the fourth layer is a ground plane located between the first and third layers and insulated therefrom for further reducing the inductance associated to the circuitry of the first layer and for substantially minimizing the circuit inductance of the third layer.

Abstract: A recording head protective overlay arrangement with an alarm capability is provided. The protective overlay is continuously replenishable between the recording surface of the recording head and the recording medium and is movable in a direction opposite to that of the recording medium so as to provide a cleaning function as well as a wear-preventive function. A dispenser cartridge housing the protective overlay is provided which is specially designed to closely conform to the recording head. A pivotable cartridge holder is included for enabling the cartridge to be inserted in a position remote from the recording head and pivotable into an operative position with the recording head. The tape medium itself and various components operatively associated therewith are pivotably mounted, to provide movement of the medium into intimate operative contact with the overlay and the recording head.

Abstract: A magnetographic copier system in which images recorded on a magnetic tape are developed by toner with magnetic properties and where the toner particles are also electrostatically charged. A piece of paper is brought into contact with the tape at a toner transfer station and a first momentary electric field of the proper polarity and orientation is then used to transfer the developed toner images from the tape to paper. The paper and tape segments with the images are then separated and are moved away from the toner transfer station. An electrode external to the transfer station is then used to apply another electric field of the same polarity to the developed toner images on the paper to prevent the toner from being disturbed by the next occurrence of the first electric field for subsequent toner images being transferred to the paper.

Abstract: Magnetographic printing apparatus includes relatively movable component supports which provide for ready access to a magnetizable recording medium when in an access position and desirably limited length travel path, when in an operative position, for a visual image recording medium adapted to receive a toner-developed image from the recording medium. One such component support is a substrate supporting selective image-producing components for collective movement between access and operative positions and defining a portion of the visual image recording medium travel path. The remaining portion of such path is defined by components fixedly supported for registry with such movable component support in such operative position.

Abstract: Improved recording head structures having lower recording current requirements and planar construction which are mass-producible with high reliability. Associated with the conductors constituting the recording elements are one or more selected materials, predeterminably situated, for substantially reducing the reluctance of the magnetic writing circuit associated to the conductor recording zone. The material is arranged to at least partially define the recording zones and to shield the recording medium from the magnetic fields associated to the recording elements outside of the recording zones. Through appropriate choice and placement of such material, a pre-biasing effect may be achieved thus enabling further reduction in recording currents.

Abstract: Apparatus is provided for uniformly premagnetizing magnetic media, such as wide magnetic tapes and/or for substantially uniformly orienting the magnetic particles in the slurry of the magnetizable layer of magnetic media during their formation. Premagnetization constitutes magnetizing the medium in a preselected direction, such as the transverse direction (i.e., perpendicular to the intended direction of movement of the recording medium past a recording head but in the plane of the medium), prior to magnetically recording information thereon. The apparatus comprises a number of predeterminably arranged small magnets disposed proximate to the medium which obviates the need for large, expensive, heavy magnets and magnet systems. A continuous transverse saturation level of magnetization is provided in the medium with virtually no vertical or longitudinal magnetic components or anomalous effects.

Abstract: Magnetographic printing, method and apparatus are used to generate letter-quality, relatively high speed transfer of magnetic toner particles from a magnetic tape to paper. A pretransfer force (f.sub.1) holding the toner to the tape is established which may be magnetic, or both magnetic and electrostatic in nature. The transfer operation employs relatively high speed approaching movement of the tape toward the paper in a controlled manner such that forces (f.sub.2) exerted on the toner particles due to the rapidly closing movement including forces created by air currents are collectively less than the toner-holding force (f.sub.1) for any instantaneous separation between the tape and paper. The operation may include the use of a bias voltage to generate a component of the electrostatic holding force and the use of a corotron to deposit electrostatic charge on the magnetic toner particles.

Abstract: An apparatus and method are disclosed for electrostatically separating a first medium such as a magnetic tape from a second medium such as paper following transfer of images from the tape to the paper. The apparatus includes a movable member or platen disposed for moving the tape into contact with and away from the paper, and a voltage source coupled across predetermined portions of the tape and platen. The method includes the step of creating an electrostatic force between the tape and platen sufficient to overcome adherence of the tape to the paper during contact of the tape with the paper, facilitating separation of the tape from the paper as the platen is moved away from the paper following image transfer. Separation is accomplished substantially independent of tape tension.