| 摘要 |
1475373 Cathode-ray tube displays IDR Inc 21 Aug 1974 [17 Jan 1974] 36822/74 Heading H4T In a video data communication system a transmitter transmits character data together with control information such as synchronizing control and address data on a character-row by character-rov basis, the character data being up-dated in real time, to a plurality of terminals each of which, by keyboard means, selects and stores a desired frame ("page") of character data (i.e. a plurality of rows of characters) for continuous display on a conventional television system display, such display being up-dated in real time. Each row of data (control, &c., and character), termed a "pseudo video scan line" comprises a self-contained packet of digital information which is transmitted in the time of one conventional television line, the information being sufficient to provide for the display of thirty-two characters in each row, sixteen such rows forming one "page". The information in each "pseudo video scan line" controls the display of between eleven and thirteen actual television scan lines on which the characters are produced in a 7 x 9 dot matrix form. Also, in addition to synchronizing, control and address data, error check information and "permission' information, i.e. information allowing the terminals to receive one or more selected groups of information, is included. The character information may be of any conventional type, e.g. news, weather, stock market, advertizing &c. and an override condition is included which allows emergency information, e.g. a civil defence warning, to be displayed at all terminals. The displays may be in colour.. |
