MULTIPLE TERMINAL DISPLAY SYSTEM

• US 3,774,158 A
• Filed: 01/06/1972
• Issued: 11/20/1973
• Est. Priority Date: 01/06/1972
• Status: Expired due to Term

• Current Assignee: Robert John Clark
• Original Assignee: Robert John Clark
• Inventors: Clark, Robert John
• Primary Examiner(s): Henon, Paul J.
• Assistant Examiner(s): Vandenburg, John P.
• Application Number:
  US05/215,817
• Time in Patent Office: 684 Days
• Field of Search: 340/172.5,324A
• US Class Current: 345/2.1
• CPC Class Codes: G06F 13/22 using successive scanning, e.g. polling G06F13/24 takes precedence
• CPC Class Codes: G06F 3/02 Input arrangements using manually operated switches, e.g. using keyboards or dials

Abstract

Blocks of digital data representing different pictures are available at a remote data processing center for supply to the control channels of a DIVCON system. Each channel includes a refresh memory for storing a block of digital data and circuits for translating the stored data to a frame of video signals but there are substantially fewer channels than display terminals. In response to a request for service by a terminal, a data channel exchange hunts for a '"'"''"'"''"'"''"'"'not busy'"'"''"'"''"'"''"'"' control channel and when it finds one, connects the channel to the terminal. The terminal may then communicate with the remote data processing center both for receiving data via the channel'"'"''"'"'s refresh memory for display on the terminal and for sending data to the remote data processing center also via the channel'"'"''"'"'s refresh memory.

Claims

1. A multiple terminal display system comprising, in combination:

means for producing digital data corresponding to different frames of video information;

m separate video display terminals, where m is a first plural integer, each of said terminals including means for selectively supplying a request for service signal;

n separate control channels coupled to said means for producing digital data, where n is a second plural integer smaller in value than said first plural integer, each of said control channels including request-for-service means responsive to a request for service signal supplied thereto from any terminal initially without service for causing an idle one of said control channels to be seized and retained by that terminal for its exclusive use only so long as that terminal continues to supply the said seized control channel with said request for service signal , and wherein each control channel includes refresh memory means for storing a block of digital data and character generator means for translating that data to a frame of video information which, in response to that control channel being seized by a terminal, is forwarded for display by its seizing terminal.

2. The system defined in claim 1, wherein said means for selectively supplying a request for service signal of any of said m terminals includes associating means for associating that terminal with a single one of said control channels at a time, wherein said request-for-service means of a control channel includes busy-determining means operative when that channel is idle for returning a not-busy signal to a terminal without service associated therewith and operative when that channel is already seized by another terminal for returning a busy signal to a terminal without service associated Therewith, and wherein an associated terminal includes signal-responsive means responsive to the return of a not-busy signal to its initial request for service for seizing that single one of said control channels with which it is then associated and responsive to the return of a busy signal to its initial request for service for associating that terminal with a different single one of said control channels.

3. The system defined in claim 2, wherein a frame of video information is composed of L display scan lines arranged in a raster, where L is a plural integer at least equal in value to m, and wherein said busy-determining means returns said not-busy signal or said busy signal during each scan line, wherein said signal-responsive means of each different terminal has a different preselected single scan line assigned thereto for responding to a not-busy signal returned thereto only during that single scan line assigned thereto, whereby a simultaneous attempt at seizing an idle control channel by more than one terminal is prevented.

4. The system defined in claim 2, wherein each terminal includes a display portion normally decoupled from said control channels, and video-signal transmission means including said associating means for extending a video connection from a control channel to the display portion of a terminal only while that control channel is seized by that terminal.

5. The system defined in claim 4, wherein each terminal includes means for generating a data signal which is normally decoupled from said control channels, and data-signal transmission means including said associating means for forwarding said data signal from a terminal to a control channel only while that control channel is seized by that terminal.

6. The system defined in claim 4, wherein each terminal includes means for generating a light-pen signal which is normally decoupled from said control channels, and light-pen signal transmission means including said associating means for forwarding said light-pen signal from a terminal to a control channel only while that control channel is seized by that terminal.

7. The system defined in claim 1, wherein each respective one of said n control channels is connected to all of said m terminals by its own set of common conductors, whereby the total number of common conductors is equal to the product of the number of members of each set multiplied by the number of control channels and is independent of the number of terminals.