General Electric Company

Charles R Stein

William C Hughes

William Thomas Hatfield

Steven Robert Koch

Neil R Shapiro

Herbert S Cole

John E Bigelow

William L Carl

A method for operating a communication network bridge is disclosed. The bridge receives a message frame from a first network connected thereto and reads the source and destination addresses of the received frame. The bridge determines if the addresses are contained in a source address table maintained thereby and if both addresses are present, discards the frame. The bridge transmits the frame to a second network connected thereto if the source address is not in the table or if the source address but not the destination address is in the table.

Local area network bridge

A bus accessing method and apparatus for the practice thereof, in a communication network, for transmitting information packets without the need for long communication periods following each transmission, is disclosed. The network comprises transmit and receive buses, a plurality of BIUs coupled between the buses, and a head-end for directing packets leaving the transmit bus onto the receive bus. Each packet has a preamble with a gap long enough to enable receiving BIUs to reset for receipt of a new packet. Each BIU in an active state with a packet to transmit measures a first time period so long as it detects no signals on the receive bus. The BIU transitions to a wait state upon completing the first time period measurement and initiates a second time period measurement. Upon completing the second time period measurement, the BIU transitions to a transmit state and initiates transmission of its packet, reverting to the active state upon completing transmission. The BIU transitions to the preempted state if upstream signals are detected during the second time period measurement or during transmission. In the preempted state the BIU measures a third time period so long as no upstream signals are detected and upon completing this measurement transitions to the transmit state.

Method and apparatus for local area networks

A direction sensitive coupling unit, and method of operation, is disclosed for use in a communication medium to indicate the presence and source direction of transmissions. A directional coupler is provided for receiving information signals from first and second directions along the medium and for providing an attenuated information signal as its output wherein the attenuation to information signals received from the first direction is greater than the attenuation to signals received from the second direction. A voltage sensitive indicating circuit is coupled to the medium and is adapted to respond to the coupler output for providing a digital indication of the presence and source direction of transmissions on the medium.

Apparatus and method for determining the source direction of local area

Apparatus for bridging between two local area networks is disclosed. The apparatus has two bridge sides each including means for receiving or transmitting a message frame, controller means for directing an incoming message frame into a memory means shared between the bridge sides or directing a frame out of the memory means for transmission, address reading means for reading an address portion of the incoming frame and processor means for determining frame transmissibility from the address portion as provided by the address reading means. The apparatus is configured such that the processor means determines incoming frame transmissibility substantially concurrent with the controller means directing the incoming frame into the memory means.

Methods for matrix addressing a liquid crystal display, utilizing the cholesteric-to-nematic phase change for information display, provides a voltage to each of a plurality of scanned electrodes. A preferred voltage waveform has a first non-zero value during an erase interval and a greater non-zero value during a display-write interval. The combined erase and write intervals occur, for each scanned electrode, once during a multiplex time interval. Each of another plurality of electrodes, arranged adjacent to the remaining surface of a liquid crystal layer and perpendicular to the scanned electrodes, are sequentially energized with a non-zero voltage having a polarity change coincident with the erase and write intervals when that portion of a display at the intersection of the first and second plurality of electrodes is to be addressed. If the inverted-polarity voltage is in phase with the scan electrode voltage, the liquid crystal material is switched to the cholesteric state and absorbs incident light, whereas if the inverted-polarity voltage is out-of-phase with the scan electrode erase-write pulse, the intersection is switched to the nematic state and incident light is transmitted through the cell substantially without attenuation.

Matrix addressing of cholesteric liquid crystal display

A liquid crystal display is provided wherein dark characters, symbols and other indicia are displayed against a light background. The electrodes of the display are driven by sinusoidal or square waveforms of multiple frequencies and/or multiple phases in manner such that the electrode leads are essentially invisible during display operation.

Liquid crystal display

A dichroic liquid crystal display of the parallel-nematic type is caused to have a bright background, indicative of the light-transmissive state, and dark characters, in the unactivated condition, by treatment of the display electrodes to cause boundaries of the dichroic liquid crystal material to be normally homeotropic except in those areas defining a character, in which areas a pattern of silicon oxide or other parallel alignment surfactant is deposited by masking techniques.

Liquid crystal display with dark characters on light background

A system of selectively controlling the light scattering areas or sites of nematic liquid crystal display devices of the type including a thin layer of the liquid crystal with conductors on opposite sides thereof, preferably transparent conductors, is described. The device is subjected to a frequency substantially above the critical frequency to maintain it in a non-light scattering state even in the presence of a voltage tending to render it light scattering. The particular sites to be rendered light scattering are selected by removing the high frequency voltage at those sites coincidentally with the application of a turn-on voltage to the same site. The circuit provides for a display of data which is utilized to control either the application of the turn-on voltage or the removal of the high frequency or hold-off voltage. The application of the other voltage to different cells or different conductors of the same cell is controlled sequentially and repetitively at a rate greater than that corresponding to the refresh time of the liquid crystal material.

Control electro-optical device utilizing liquid crystal

A method for the non-scanned matrix addressing of bar displays, particularly of the liquid crystal type, for driving all 'on' elements of the display to full optical saturation and, hence, achieving uniform brightness and contrast, comprising the steps of driving the common electrodes of subordinate, 'full-on' blocks of data segments with a first waveform of amplitude and frequency differing from the data signal waveform; driving the common electrode of a transitional, 'top-of-the-bar' block of data segments with a second waveform of amplitude and frequency similar to a data signal waveform; and driving the common electrodes of the uppermost, 'off' blocks of data segments with a waveform of frequency higher than the display cut-off frequency. Apparatus is disclosed for generating and switching the required waveforms to facilitate use of such a bar display.

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Schenectady, NY, United States of America

Charles R Stein