Abstract: A cursor control device having particular application to a computer display system is disclosed. The cursor control includes a unitary frame, having a domed portion substantially surrounding and retaining a ball which is free to rotate. X-Y position indicating means are provided, such that rotation of the ball provides signals indicative of X-Y positions on the display system. The ball is free to "float" in the vertical direction within the dome, and thereby maintain good surface contact. X-Y positions are established by movement of the control device over a surface. A display system and method is disclosed for use in conjunction with the cursor control device, which permits a user to select command options simply by movement of the displayed cursor over a "pull-down" menu bar.

Abstract: A waveform of arbitrary complexity may be generated using a minimal number of circuit elements and minimal complexity by generating a frequency domain from a minimum set of base frequencies by storing lower octave frequencies of the minimal base set within a note memory. Selected octave and pitch, or note may be read from the note memory according to a list of notes to be thusly read as stored within a note list memory. Each of the instantaneous values of the base frequencies read from the note memory is then added in an accumulator to represent the instantaneous value of the sum of notes or tones comprising the complex frequency at that time. The application of process time periods will replicate an arbitrary complex waveform. Such a frequency generator can find wide application within electronic musical devices, tests and analysis instrumentation, communications and many other fields.

Abstract: A microcomputer system with video display capability, particularly suited for small business applications and home use is described. The CPU performance is enhanced by permitting zero page data to be stored throughout the memory. The circuitry permitting this capability also provides a pointer for improved direct memory access. Through unique circuitry resembling "bank switching" improved memory mapping is obtained. Four-bit digital signals are converted to an AC chroma signal and a separate luminance signal for display modes. Display modes include high resolution modes, one of which displays 80 characters per line.

Abstract: A device which provides a plurality of actuator members, for effecting switch closure in a sandwich keyboard formed with a printed circuit board having many electrical conductive paths thereon, with the actuator members being integrally formed with a connecting bus. The device is provided with a number of bendable fingers for making contact with any desired conductive path lying beneath the fingers thereby permitting the device to serve as a "jumper connector" without adding wire jumpers to the back of the printed circuit board. The actuator member is constructed to have self cleaning contact surfaces. A plurality of such actuators is preferably formed of a single strip of thin sheet metal.

Abstract: A circuit for generating a control signal for use in a communication line duplexer or other isolation means. The transmitted signal at the output of the duplexer is phase detected to detect its real and imaginary components. These components are used to modulate the transmitted signal which is then injected into a feedback loop of the duplexer. This substantially cancels the transmitted signal at the output of the duplexer. The circuit permits the communication line to be terminated in a constant impedance.

Abstract: A microcomputer including a video generator and timing means which provides color and high resolution graphics on a standard, raster scanned, cathode ray tube is disclosed. A horizontal synchronization counter is synchronized at an odd-submultiple of the color subcarrier reference frequency. A "delayed" count is employed in the horizontal synchronization counter to compensate for color subcarrier phase reversals between lines. This permits vertically aligned color graphics without substantially altering the standard horizontal synchronization frequency. Video color signals are generated directly from digital signals by employing a recirculating shift register.

Abstract: An apparatus for digitally controlling the display of color in a phase alternation line (PAL) video display is disclosed. Coded digital signals are shifted in a recirculating shift register. The direction of shifting in the register and the stage at which the signals in the register are sensed are changed as a function of odd/even display lines to compensate for PAL phase reversals.

Abstract: A controller for interfacing between a digital computer and a magnetic disc recorder, such as a "floppy" disc, or other recorder or memory is disclosed. The controller, which permits accessing of the disc with minimum control by the computer, is realized with relatively few components and is particularly suited for interfacing between a microcomputer and a "minifloppy". Track selection with a computed velocity profile is employed. Synchronization with a soft sectored disc is achieved without additional hardware.

Abstract: A microcomputer including a video generator and timing means which provides color and high resolution graphics on a standard, raster scanned, cathode ray tube is disclosed. A horizontal synchronization counter is synchronized at an odd-submultiple of the color subcarrier reference frequency. A "delayed" count is employed in the horizontal synchronization counter to compensate for color subcarrier phase reversals between lines for the non-interlaced fields. This permits vertically aligned color graphics without substantially altering the standard horizontal synchronization frequency. Video color signals are generated directly from digital signals by employing a recirculating shift register.

Abstract: A direct current (DC) power supply of the single-ended flyback type particularly suited for providing power for integrated circuits is described. The power supply is self-exciting and thus does not employ an auxiliary drive or oscillator. The starting/restarting circuitry provides protection against faults. Because of this fault protection, a relatively simple over-voltage circuit is employed at the output of the supply. An additional primary winding is used to provide protection for no-load conditions.