# US 5,704,042 A · Accelerated replication of multiple computer displays > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,704,042 A - Document ID: US5704042A - Status: Granted - Kind: A - Application number: 08/128,012 - Filed: 1993-09-28 - Granted: 1997-12-30 - Earliest claimed: 1993-03-19 - Assignees: NCR Corporation - Inventors: John Hester; Krista S. Schwartz - Web page: https://patentgrep.com/patent/US5704042A ## CPC - G06F 3/038: Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry - G06F 3/0481: based on specific properties of the displayed interaction object or a metaphor-based environment, e.g. interaction with desktop elements like windows or icons, or assisted by a cursor's changing behaviour or appearance - G06F 3/1454: {involving copying of the display data of a local workstation or window to a remote workstation or window so that an actual copy of the data is displayed simultaneously on two or more displays, e.g. teledisplay} - H04L 12/1827: {Network arrangements for conference optimisation or adaptation} - H04L 65/403: Arrangements for multi-party communication, e.g. for conferences (data switching systems for conference H04L12/18; arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities H04M3/56; television conferencing systems H04N7/15) - H04L 67/1095: Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes - H04L 67/75: Indicating network or usage conditions on the user display - H04N 7/15: Conference systems - G09G 2360/04: Display device controller operating with a plurality of display units - H04L 67/131: Protocols for games, networked simulations or virtual reality - H04L 69/329: in the application layer [OSI layer 7] - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A system wherein multiple computers engage in a video conference. The invention creates a common visual image which is displayed by all computers. However, the invention does not distribute a bit map of the image to all computers. Instead, the invention distributes the commands from which the image is created. Further, the distributed commands rely on data structures, which define parameters such as pen color, background color, line width, etc. The data structures are stored in each computer. When a data structure is changed, the invention does not immediately inform all other computers of the change, but waits until necessary. ## Claims ### Claim 1 In a system wherein a GUI runs on a host computer and generates graphic images by issuing GDI calls which make reference to device contexts, the improvement comprising: a) maintaining similar device contexts in remote computers and b) maintaining substantially identical first program means on each computer, which i) allows a single application program to selectively run on any of the computers, and no other computer, which generates a display on the selected computers, ii) replicates the display on all other computers, iii) allows a user of each computer to make annotations, containing graphical images, on the replicated display of each respective computer, iv) allows each respective user to selectively A) cause the first program means to copy the annotations made by the user to replicated displays of other computers, or B) cause the first program means to refrain from copying the annotations made by the user. ### Claim 2 (depends on 1) An improvement according to claim 1 and further comprising the step of transmitting changes in the host's device contexts to the remote computers, without redundancy. ### Claim 3 (depends on 2) An improvement according to claim 2 and further comprising the step of transmitting the changes only after a GDI call was issued which requires a changed device context. ### Claim 4 (depends on 1) System according to claim 1, and further comprising: c) informing a new remote computer, which connects with the host and said remote computers while said application program is running, of the current status of the device contexts. ### Claim 5 A system comprising a) multiple computers which use data records identified as device contexts, together with other data, to generate drawings; b) means for maintaining common contents in corresponding device contexts in different computers; and c) a first program means, running on each computer, for i) allowing an application program, different from the first program means, to run on any one of the computers, and no other; ii) copying displayed output of the application program to displays of all other computers; iii) allowing a user of every computer to apply annotations, which contain text and graphical images, to the copied display output of the user's computer; and iv) allowing each respective user to selectively A) cause the first program means to copy the annotations made by the user to copied displayed output of other computers, or B) cause the first program means to refrain from copying the annotations made by the user. ### Claim 6 (depends on 5) A system according to claim 5 in which the means for maintaining c) detects changes in a predetermined device context; and d) notifies other computers of the changes. ### Claim 7 (depends on 6) A system according to claim 6 in which the notification is done without transmitting redundant data. ### Claim 8 (depends on 5) System according to claim 5, and further comprising: c) means for informing a computer, which connects with the multiple computers while said application program is running, of the current status of the device contexts.