| 摘要 |
In a Teletext transmission system data is transmitted in digital form during lines in the field blanking period of the composite video signal of a television transmission. On reception the information is decoded to generate a display comprising a page having a predetermined number of rows of information in alphanumeric or graphics form. The data is received in blocks comprising information digits each block associated with a respective group of two-part address inputs, one part providing page identification and the other data row information. A plurality of serially accessed data storage registers is provided for the data rows, each uniquely corresponding to a selected one of the two-part address digits. A decoder is responsive to transmitted address data to independently address the corresponding shift register via a first switch to write data into the store and is responsive to address data to read data from a selected register via a second switch for display generation. Data entered into the shift register may be recirculated until required for display. Transmission of data rows out of page and row number sequence is thus accommodated so that only data rows containing information and data rows needing updating need be transmitted.
|
