Abstract: The effects of impulse noise on the operation of a microprocessor-controlled Loran-C receiver are reduced by muting or attenuating the received signals in the front end of the receiver ahead of the receiver gain during a time period which preceeds the start time of the pulses being tracked. The attenuation is selectively removed after the start time of each pulse being tracked to permit the receiver to perform its time difference of pulse arrival measurements in the normal manner. The attenuation is also selectively removed during those time periods in which the receiver performs its envelope slope, skywave/groundwave and other such samplings. The attenuation is provided by a muting circuit which is controlled by a time gate signal that derives from the microprocessor of the receiver.

Abstract: A D-type flip-flop (10) receives the D input on an input line (14) of a transfer gate (12) that also receives the flip-flop clock signal. A state gate (20) forwards the transmission-gate output when the signals on two of its input lines (22) and (24) remain true. To reset the flip-flop asynchronously, a false signal is imposed on one of the input lines (22) of the state gate (20). By coordination of a second clock signal, which is applied to a second transmission gate (34), with the reset signal, the reset condition is held until the next clock pulse on the first transmission gate (12). The flip-flop ordinarily operates as a dynamic circuit, but, in order to maintain the reset condition in circumstances in which the reset state is to be maintained for an extended period of time, a latch gate (26) is enabled by a true signal on one of its input lines (32) to feed the reset output of the state gate 20 to one of its input terminals (24 ) so as to latch the flip-flop in the reset state.

Abstract: A data stack for storing data at sequential locations in a memory and for transmitting the data in modes defined by commands from a host data processing system. A random access memory stores the data in sequential locations at addresses selected by a state signal generator comprising read only memory. The state generator generates the addresses and read/write control signals for the random access memory in response to the commands from the host system and a previous address provided by the generator.

Abstract: A mechanism for clamping the leading edge of a sheet to be wrapped around a printing drum for printing in a plurality of colors includes a clip that is movably mounted in the drum so that it can be moved between an open position and a clamping position, the clip being biased to its clamping position. One or more deflectable cams are positioned adjacent to the drum for engagement by the clip. When the drum is rotated in its direction for printing successive colors on the sheet, the clip deflects the cam and remains in its clamping position. However, when the drum is rotated in the opposite direction to discharge a printed sheet, the clip is engaged by the cams and wedged thereby to its open position thereby releasing the printed sheet. The mechanism also includes provision for automatically discharging the printed sheet from the drum to a discharge path adjacent to the drum when the clip is opened.

Abstract: A drive roll 14 carries a gear (60) that engages a reversing gear (58) driven by a planetary gear (56) on a pivot arm (50). The planetary gear (56) is driven by a sun gear (48) that rotates about the pivot axis of the pivot arm (50) and in turn is driven ultimately by a motor (30). A unidirectioal roller clutch (52) is connected between the pivot arm (50) and the sun gear (48) so as to permit relative rotation between the sun gear and the pivot arm in one direction but prevent it in the other direction. As a result, when the sun gear (48) is driven in one direction, it permits the pivot arm to remain in the position in which the planetary gear (56) engages the reversing gear (58). When the sun gear (48) is driven in the other direction, on the other hand, the pivot arm (50) is caused to pivot with rotation at the sun gear (48) to bring the planetary gear (56) out of engagement with the reversing gear (58).

Abstract: A bit-slice adder circuit for adding a plurality of input numbers in binary form. A tally circuit receives all of the bits from a bit position of all of the numbers and identifies the number of "ones" in that bit position. This information is coupled as address signals to a memory, which also receives, as address signals, carry signals. Each storage location at each address in the memory stores the sum of the carry portion of the location's address and the "ones" portion of the address signals from the tally circuit. The least significant bit of the addressed storage location is coupled to a shift register, and the remaining bits comprise the carry signals that are coupled to the memory's address input for the next signal from the tally circuit. After all of the bit positions in the input numbers have been coupled through the tally circuit, the sum is generated which comprises the last carry signal concatenated with the bits stored in the shift register.

Abstract: Universal logic circuit cells for use in designing and laying out electronic circuits. The cells provide AND and OR on other logical functions on input signals, and include a conventional AND or OR gate, or other logic gate, and associated input and output connections and circuitry that enables them to be used in many applications. The cells simplify laying out a combinatorial logic circuit after it has been designed.

Abstract: A graphics drum plotter in which wide strip paper is divided into virtual columns. An operator interface is provided whereby an operator can define the size and number of columns across the strip paper. Instead of producing a series of small plots along one edge of the wide strip, the system includes logic to place the series of plots sequentially across the columns of the strip paper before advancing the strip paper to a next writing area. A paper slitter is also provided to slit the paper on the column lines after the printing thereon.

Abstract: A thermal printer of the three-pass variety for printing in color featuring a sheet feeder, automatic registration, and ejection of the sheet when printing is complete. A rotatable, cylindrical drum has the print head close adjacent thereto and includes a releasable clamp for receiving the paper from the sheet feeder. The paper is clamped to the drum and the drum rotated past the print head three times, one for each color. The drum is then rotated to release and eject the paper. Sensors are provided to detect and monitor the position of the drum during its printing operation and to monitor the status of the paper supplied to the clamping mechanism.

Abstract: An X, Y plotter particularly adapted to use both cut paper and strip paper. A driven roller provides motion of the paper back and forth according to one signal. A moveable pen block containing the pen is moved transverse the path of the paper in response to the second signal, thus providing controlled motion in the X and Y directions. According to one aspect, an idler roller is provided parallel to the driven roller around which an endless belt is disposed to be driven in combination with the drive roller by two pairs of rows of sprockets on the driven roller adapted to mate with holes provided therefor in the belt. Cut paper temporarily attached to the belt with drafting tape or the like is moved beneath the pen for plotting purposes. The inner row of sprockets is adapted for engaging holes in strip paper for moving it beneath the pen.

Abstract: An easily adjustable and automatically aligning pinch roller assembly for use in a graphics plotter. A movable carriage hangs from a supplemental inverted T-shaped track below the main carriage track of the plotter. The pinch roller is pivotally attached to an arm from the carriage. A leaf spring on the carriage pulls the carriage loosely into positional alignment with the pinch roller aligned with the drum while allowing translational movement easily. A second bias spring urges the pinch roller down and the carriage into gripping engagement with the supplemental track with sufficient force to prevent translational movement thereof. A release bar holds the pinch roller off the drum and releases the gripping force to allow the carriage to be slid for adjustment.

Abstract: A universal logic circuit that performs a selected one of several logic operations on a pair of input signals in response to the receipt of a control signal and the terminals to which the input signals and control signal are coupled.

Abstract: An improved wire grid glass tablet for digitizing graphic information which includes a glass plate with a resin layer bonded to one side and having orthogonal grids of wires, made of a ductile material which is stretched beyond the yield point, embedded in the resin layer near the surface thereof to maximize signal-to-noise ratio coupling to the wires.

Abstract: A liquid toner applicator includes a hollow housing or manifold divided into two channels. A wall of the housing common to both channels is composed of a multi-layer lamination of thin sheet layers, such as etched metal foils. The outermost wall layer constituting the bearing surface for the recording medium is formed with a pattern of slots for applying toner to the exposure surface of the medium. The innermost wall layer is formed with two sets of holes, each set being open to different housing channels. The remaining wall layers between the innermost and outermost layers are each formed with an array of slots or holes which combine and interconnect in the wall lamination to provide a first network of precisely defined toner feed pathways between one of the housing channels and one end of each of the slots in the outermost wall layer and a second network of precisely defined toner recovery pathways between the opposite end of each of the slots in the outermost layer and the other housing channel.

Abstract: A high-frequency, high-power generator of the type in which energy is stored in the capacitance of a transmission line and then discharged into a load by the action of a spark discharge device. The load is connected between one end of a transmission line conductor and ground and the other end of the same conductor is grounded. The line is folded and both ends of the other transmission line conductor are connected to the spark discharge device. A charging circuit applies a voltage to the latter conductor and when it reaches the discharge potential of the spark discharge device, the latter discharges to connect both ends of that conductor to ground. This provides relatively well-defined positive and negative pulses to the load.

Abstract: An electronic writing pen which induces electromagnetic signals in conductors which are disposed in a writing table and are connected to digitizer circuitry is disclosed. The pen has a writing cartridge which is movable within the pen housing and includes, in one embodiment, a thin, deformable, stainless steel dome switch element which functions as an electrical contact in a normally-open switch which is utilized to provide an electrical indication of the up/down status of the pen to the digitizer and tactile feel of change of pen position to the pen user. In another embodiment, the switch includes an insulating strip having a conductive layer thereon to provide status indication with low application of force to the pen and without tactile feel.

Abstract: Apparatus for assisting in the loading of strip roll paper in a graphics drum plotter having a vacuum column disposed between a strip paper supply roller and a drum wherein insufficient space is available between the drum and the beam/writing head above it for reaching through to grasp the paper on the supply roller for pulling it through. A hook-shaped wire guide is hingedly attached through a slot in the center of the back wall of the vacuum column. The guide wire is biased by a counter weight to a position within the vacuum column and is moved out of the vacuum column through the slot from the force of paper descending into the vacuum column. The hook is shaped to guide paper being rolled off the supply roller across the space between the front and back walls of the vacuum column and to direct it into a position between the drum and the beam/writing head where it can be grasped.

Abstract: A turret head for use in a graphics plotter for holding a plurality of liquid ink pens adjacent the point of writing and for selectively changing the pens to be the writing pen. Automatic pen tip capping and uncapping is included. A plurality of spaced radial arms are mounted on a turret driven by a stepping motor between main positions. A pen holder assembly is mounted for vertical movement between raised and lowered positions and carries a pen gripping arm thereon. The pen gripping arm is adapted to move vertically between the radial arms of the turret and beneath them as the turret is rotated. The arms are provided with facing releasable gripping fingers for exchanging pens between arms upon contact.

Abstract: An improved wire grid glass tablet for digitizing graphic information which includes a glass plate with a resin layer bonded to one side and having orthogonal grids of wires, made of a ductile material which is stretched beyond the yield point, embedded in the resin layer near the surface thereof to maximize signal-to-noise ratio coupling to the wires.

Abstract: LORAN-C navigation apparatus is disclosed wherein digital circuitry and a microprocessor .[.is.]. .Iadd.are .Iaddend.used to automatically identify LORAN transmitting stations and .[.makes.]. .Iadd.make .Iaddend.standard hyberbolic navigation measurements. The equipment operator manually enters the group repetition rate into the apparatus for a LORAN-C chain covering the area within which the navigation apparatus is being operated. Initially, the apparatus searches all incoming signals .Iadd.as they are received .Iaddend.until signals from a master station are received regularly at the stored group repetition rate.