Abstract: A communication protocol includes a hierarchical arrangement of time slots within a communication channel for transmission and reception of isochronous data (e.g., video, audio, etc.) between components of a computer network. One of the time slots may include a window for transmission of keyboard and/or cursor control data from a client unit to a server, for example as a series of past and present keyboard and/or cursor control entries, with these entries being accompanied by a counter value indicative of the number of new entries since a previous transmission. Audio rate control information may also be transmitted from the client unit to the server during the reverse time slot and may be used by the server to determine the amount of audio information to be transmitted to the client unit in a subsequent forward time slot transmission period. The audio rate control information is determined according to the amount of stored audio information at the client unit.

Abstract: A converter for converting digital data into differential analog signals includes a temperature and process independent bias voltage generator for generating a bias voltage and a digital to differential converter for converting a digital word into differential voltages. The digital to differential converter includes a first switching circuitry controlled by the digital word for selectively coupling a first output node to the bias voltage and a second output node to a supply voltage. Second switching circuitry controlled by a complement of the digital word selectively couples the first output node to the supply voltage and the second output node to the bias voltage. The first and second pairs of switches substantially simultaneously conduct at a desired differential cross-over voltage at the first and second output nodes based on the choice of the bias voltage such that the digital to differential analog converter operates from the operating voltage to the operating voltage plus the bias voltage range.

Abstract: A pipe spinning apparatus connected in a drilling string for threadably connecting or disconnecting joints of pipes is provided. The pipe spinning apparatus includes a rotatable stem for connecting and disconnecting members, at least one pneumatic, turbine motor rotatably connected to the stem and a throttle control functionally connected to the turbine motor for variably controlling the speed of rotation of the stem. The rotational speed of the stem can be controlled through a range of revolutions per minute (rpm) depending on the air pressure and flow rate provided. The speed may be varied from 0 rpms to at least 500 rpms. A desirable range of operation is from 0 to 200 rpms. This ability to control and vary the speed of the stem greatly increases the safe operation of present kelly spinner over the prior art kelly spinners.

Abstract: An image projection system comprises an image projector, such as a film or television projector and a projection screen. The projection screen is fabricated of a substantially transparent material, such as glass or plastic. The screen of transparent material has one or more areas or portions formed therein which areas or portions may be made to be translucent upon the application of a stimulus. Once in a translucent condition, the projected image can be received and viewed on the translucent portion.

Abstract: An apparatus and method for verifying a process step in the fabrication of an integrated circuit device is implemented. A ring oscillator is fabricated on the dice constituting the integrated circuit device being manufactured. The ring oscillator structure is adapted for sensitizing the ring oscillator to variations in the process step being verified. During test of the wafer containing the dice, a scan of the frequency of the ring oscillator across the wafer for each die under test is made. Deviations in the ring oscillator frequency from a preselected nominal value delimit regions of the wafer for which the process step is marginal.