Abstract: In a direct digital synthesizer providing a frequency modulated output the modulation input is bit shifted and the rate of the direct digital synthesizer phase accumulation is controlled to provide enhanced FM deviation resolution.

Abstract: A pixel processor converts data indicating origin, direction, length and intensity of each of a set of lines forming a picture into a half tone bit map on the picture. The pixel processor organizes the picture into an array of similar half tone cells, each half tone cell being a rectangular array of pixels, by storing adjustable data indicating the size of a half tone cell and a pixel intensity threshold level for each pixel of a half tone cell. When processing each line, the pixel processor reads pixel data words out of the bit map, each pixel data word including at least one bit corresponding to a pixel along the path of the line. For each such bit, the pixel processor determines the half tone cell position of the corresponding pixel, determines whether the pixel intensity threshold level assigned to that half tone cell position is lower than the intensity level of the line and sets the state of the bit accordingly.

Abstract: The frequency resolution of a direct digital synthesizer is increased by varying the phase increment used to accumulate wave lookup table addresses between two integer values. The time periods during which the larger integer value is employed is proportional to a fractional part of the desired phase increment for providing an analog output at a selected frequency.

Abstract: Stages of a graphics data processing pipeline are interconnected by a common bus for conveying data and arbitration signals to and from each stage. Each data transmitting stage arbitrates for and acquires control of the bus when it has output data to transmit to an addressable storage location within a next stage. Each pipeline stage other than a first stage generates a BUSY bit indicating whether it is processing data or awaiting new input data from its preceding stage. When one pipeline stage has output data to transmit to a next pipeline stage, the transmitting stage periodically polls the receiving stage by acquiring control of the bus and placing on the bus a particular address associated with the next stage. Whenever the next stage detects the presence of the particular address on the bus, it places its BUSY bit on the data lines of the bus.

Abstract: A triggering control circuit varies a holdoff period for one sweep cycle whereby to lock triggering to a different, selected event viewable on an oscilloscope.

Abstract: A digital oscilloscope includes an acquisition system for digitizing an input signal to produce and store in memory a waveform data sequence representing the input signal. A display system within the instrument reads out and processes the data stored in the memory to produce a waveform display representing the input signal. The instrument responds to an input "erase" command from a user by overwriting the waveform data sequence stored in memory with a predetermined data sequence defining an easily recognizable display pattern. The oscilloscope thereafter performs a checksum operation on overwritten portions of memory to determine whether the overwrite operation was successful, and displays an indication of overwrite success on its screen.

Abstract: A data transfer driver transfers multiple byte data words supplied by a data processing device to a peripheral device as a sequence of single data bytes. The driver operates selectively in either a handshaking mode, wherein data bytes are transferred to the peripheral device asynchronously in response to handshaking signals from the peripheral device, or in a streaming mode where data bytes are transferred to the peripheral device periodically. The driver includes circuitry that permits the data processing device to check the operation of the driver and to monitor handshaking signals produced by the peripheral device.

Abstract: A dispenser cathode body includes a heat capturing portion extending rearwardly from the dispenser cathode, said heat capturing portion having greater mass and thickness than an exterior support skirt. A slip-in heater is received within the heat capturing portion. Substantially greater electron emission density is secured without requiring injuriously high temperatures from the slip-in heater.

Abstract: A low distortion light source comprising a light emitting diode and a compensating diode connected in parallel with respect to a D.C. bias current and in anti-series with respect to an A.C. signal source. The compensating diode is selected to have a forward resistance similar to the forward resistance of the LED. Adjusting the D.C. bias current through the diodes to be approximately equal matches the forward resistance characteristics and substantially reduces the undesired intermodulation products.

Abstract: A frequency response stabilized amplitude modulation circuit includes a variable gain amplitude modulator producing an output signal having an amplitude proportional to a product of amplitudes of input carrier, modulating and gain control signals. An envelope detector generates a signal having an amplitude responsive to the modulation envelope of the output signal. A first difference amplifier produces the modulating signal input to the amplitude modulator in proportion to a difference between amplitudes of the envelope detection signal and an audio input signal. The modulating signal incorporates negative feedback to ensure the envelope amplitude of the modulated output signal tracks the audio input. A second difference amplifier provides the gain control signal input for the amplitude modulator in accordance with a difference between amplitudes of the modulating signal, scaled by a constant factor, and the envelope detection signal.

Abstract: A single-ended to differential coupling device includes an input coaxial transmission line feeding sections of output coaxial transmission line across a break or gap between the outer conductors of the output transmission lines. A shunt resistor across the input transmission line and a series resistor interposed between the center conductors of the output transmission lines provide exact impedance matching in conjunction with plural ferrite toroids disposed about at least one of the transmission lines to prevent shorting of the input signal.

Abstract: A circuit board configuration for I/O devices and logic devices, wherein the I/O devices have current levels substantially higher than the current levels associated with the logic devices. The I/O devices are grouped adjacent a connector, and a ground return plane surrounds the I/O devices coupling the ground terminals of the I/O devices to the ground pins of the connector. The logic devices are spaced some distance away from the connector where the ground terminals of the logic devices are connected through vias to a ground plane. The ground return plane, forming a strip line with the ground, plane, is effective for isolating the I/O devices and reducing signal distortion on the board.

Abstract: The trajectory across a surface of an intended target point of a moving beam directed toward the surface is digitized by finding a particular point along each of a plurality of parallel axes of the surface for which a two-dimensional convolution integral of two functions is a maximum. A first of the two functions is the instantaneous intensity distribution of the beam on the surface with respect to the instantaneous position of the target point on the surface. The second function is the average beam intensity distribution on the surface produced as the beam moves across the surface during a finite period. A digital data sequence is generated in which each element thereof represents the position on the surface of a separate one of the particular points determined in this fashion, and this sequence represents the trajectory of the target point of the beam on the surface.

Abstract: A "diagramming debugger" creates a graphical representation of the sequence of messages sent during operation of an object-oriented program. When one object transmits a message to another object, the diagramming debugger displays representations of the transmitting and receiving objects on a computer screen, each representation comprising a box with labels identifying the represented object. The box representing a sending object includes therewithin a symbol (comprising, for example, one or more characters) identifying the method that sent the message, while the box representing the receiving object includes therewithin a symbol identifying the method invoked by the message. The message is represented by an arrow pointing from the symbol identifying the sending method to the symbol identifying the invoked method.

Abstract: Operation of a microcomputer-based instrument is controlled by software including a control interface system, a command execution system, and a steady state system. The steady state system includes a group of subsystems operating as concurrent tasks, each carrying out various instrument operations. The control interface system includes a set of subsystems, each responsive to configuration control input signals from a separate control signal source, and each converting configuration control signals into "configuration commands". Each command identifies a particular procedure for configuring the operating state of one or more instrument hardware or software steady state subsystems of the instrument. Each command is stored in memory in one of several queues (one for each control interface subsystem) until the procedure it invokes is carried out.

Abstract: A delay time between the start of a trace on an oscilloscope screen and a point along the trace is computed based on measured "sweep gain" and "sweep start" parameters characterizing a triggered sweep signal controlling the horizontal position of an electron beam creating the trace, the sweep signal increasing when triggered from a starting level at a constant slew rate to move the beam at a constant speed across the screen. The sweep start parameter is the value of input data applied to a digital-to-analog converter (DAC) which would cause the DAC to produce an output voltage equal to the sweep signal starting level, and the sweep gain indicates the rate of increase in DAC input data required to produce a DAC output signal with a rate of increase similar to the slew rate of the sweep signal. The horizontal position of the point along the trace is the beam position on the screen at the moment the sweep signal magnitude reaches the magnitude of the DAC output signal.

Abstract: An integrated support structure provides for improved mounting of components such as circuit boards, disk drives, power supplies, and the like. The structure includes an upper frame and a lower frame hinged together and having cooperative elements for capturing components therebetween as the upper frame and lower frame are brought adjacent to one another in parallel relation. A sliding guide and bridge beam clip secure a disk drive to the structure while a hook and spring latch mount a power supply. The frames are suitably formed by structural foam injection molding and the components are secured to the structure without the need for screws. The entire assembly may be inserted in a shell or case for protection thereof. The overall configuration allows rapid assembly for production and rapid disassembly for service.

Abstract: In a cascaded system of finite-duration impulse response filters, the transfer function of each filter relating its output data sequence to its input data sequence is selected such that elements of its output data sequence are in phase with the first element of its input data sequence. Operation of each filter other than the first cascaded filter is suppressed until it receives from the preceding filter, the first output data sequence element which is in phase with the first element of the input data sequence of the preceding stage, thereby ensuring that the first element of the output data sequence of the first filter is in phase with the first element of the input sequence to the first filter.

Abstract: An interface circuit in a modular electronic system includes duplex control-signal transmission lines. Modules connectable to a controller unit of the system transmit configuration data items by way of the duplex lines to the controller during a first time period, and the controller during a second time period generates module control signals in accordance with the configuration of the modules. The module control signals are transmitted to the modules on the duplex transmission lines.

Abstract: Menus displayed on a screen of an instrument permit an operator to adjust and monitor the operating state of the instrument. Various menus are added and removed from the display in response to changes in the operating state of the instrument so that those menus appropriate for the operating state of the instrument are automatically displayed while inappropriate menus are automatically removed from the display. Displayed menu items may be added, removed or modified in response to changes in the operating state of the instrument, as evidenced by changes in the configuration parameters, so that only those menu items which are appropriate to a given operating state are displayed.