University of Illinois

Paul T Tucker

Donald L Bitzer

William E Keasler

Robert K Rader

David M Andersen

Bruce A Sherwood

An improved computer based education system maintains rapid response to user input without limits to the number of stations. The system incorporates a dedicated processor at each user station so that the user station receives executable code as opposed to a display map. To support plural users a cluster subsystem is provided interconnected to the user stations via a high speed bidirectional communication subsystem. The cluster also includes a mass storage device, a high speed buffer, communications interface and at least one processor for serving user requests.

Cluster computer based education delivery system

A modem capable of achieving essentially 9600 bit per second information transfer rate through the switched telephone network. The high bit rate is achieved notwithstanding the variations in the characteristics of the switched telephone network by phase and amplitude modulating a plurality of sub-carriers at a relatively low baud rate. Correlation detection is employed at the receiver to extract or demodulate the information contained in the various sub-carriers. To allow correlation detection with orthogonal signals, each of the sub-carriers is harmonically related to a fundamental which fundamental is, however, slightly higher than the baud rate. This allows the receiver to delay correlation for a 'gap' time, which reduces the effect of transients produced by modulation and also provides greater tolerance to inter-symbol distortion. Since the fundamental of all the sub-carriers is higher than the baud rate, the receiver 'sees' orthogonal signals during the integration or correlation time which is maintained as the period of the fundamental. In addition to the information sub-carriers, a pair of unmodulated sub-carriers are also transmitted to enable the receiver to maintain the correlation interval in proper synchronization with the transmitter, and to correct for phase distortion and frequency offset.

High speed modem suitable for operating with a switched network

A time-voltage multiplexing system for addressing a particular cell or location on a gas discharge plasma panel in which a group of panel electrodes are charged to the cell voltage firing level but only one electrode of the group is allowed to remain charged for a time duration sufficient for selective discharging of the desired cell. A multiple secondary transformer embodiment incorporating the time-voltage multiplexing addressing system. A method and apparatus for increasing the usable range of sustaining signals for plasma panels by applying a narrow width boost pulse to the panel within a selected time immediately after the initiated sustaining discharge, including means for varying the boost pulse amplitude, width and position with respect to the sustaining discharge so that the usable sustaining signal range can be optimized for a particular plasma panel.

Growing community of inventors

Urbana, IL, United States of America

Paul T Tucker