In the United Kingdom there is a widely used information system known as teletext. It is also used in many other countries.
Teletext is a digital technology used in conjunction with analogue television systems. Digital information is inserted in several of the otherwise unused lines of the television signal within what is known as the vertical blanking interval of the television picture. In the United Kingdom the government is to eventually switch off all analogue television broadcasts, as part of the already started process of migration to digital television technology. Thus teletext in its present form will finish. There are digital television text and graphics displaying systems which may continue the teletext name, yet the original teletext display format is likely to go. Teletext started in the early 1970s and the currently implemented specification essentially dates from 1976, (with the exception of the later fast text linking system). The government is thinking in terms of turning off the analogue transmissions sometime between 2006 and 2010. I am thinking that it would be a good idea to encode the archive copies of teletext pages that exist into a Unicode compatible format for the future. Teletext has been around for about a quarter of a century in more or less its present form and within another quarter of a century that form might well be gone completely. I have looked in the Unicode mail list archive and found various items about encoding teletext pages using existing Unicode characters. I am here suggesting a different approach, a teletext archiving approach. I suggest that, in a discussion within this mailing list, a Private Use Area encoding for archiving teletext pages is agreed, with a view that eventually it will be put as a proposal for promotion to regular Unicode, probably into one of the higher planes. The reason for this approach is that it will permit teletext pages to be encoded in a plain text file within a document which discusses the technology. The teletext characters need to be implemented with the same width as each other, whereas characters in a discussion document need to be displayable with possibly different widths one from another. I suggest, as a starting point for a discussion the following. U+E200 through to U+E27F for the United Kingdom teletext character set 0x00 to 0x7F. U+E280 through to U+E2FF to be used to define teletext characters defined in other countries where those characters are not the same as in the United Kingdom character set. This means all of the German accented characters and so on. The notes for each encoding to include details of the location within the 0x00 to 0x7F range where that character was originally encoded and in which country or countries it was so encoded. All teletext pages could then be encoded using the above characters. In addition, the following could be used. Where a character is to be displayed in contiguous graphics mode, and is a graphic, not a capital letter push through, the character may be represented using U+E320 to U+E33F and U+E360 and U+E37F. Where a character is to be displayed in separated graphics mode, and is a graphic, not a capital letter push through, the character may be represented using U+E3A0 to U+E3BF and U+E3E0 and U+E3FF. This will enable a good idea of the look of a teletext page to be displayed using an ordinary TrueType font in a wordprocessing document. Naturally there is also scope for special teletext displaying programs to be produced so that graphics with different combinations of foreground and background colours can be displayed properly. I feel that this encoding will be useful as a stepping stone to a permanent regular Unicode encoding of teletext characters for archiving purposes. Hopefully this initiative will encourage people to get out any old 5 1/4 inch floppy discs that they may have and transfer any teletext pages saved upon them into an archived form. Readers interested in teletext might like to have a look at the following. http://teletext.mb21.co.uk I am hopeful that by having a specific encoding within Unicode for teletext that the archives of teletext pages that exist will be conserved for posterity and that an important aspect of social history will be preserved for the future. Does anyone know if the early graphic art from Oracle (Oracle being the name of the then ITV teletext service as well as of the technology, being an acronym for Optional Reception of Announcements by Coded Line Electronics) in the mid 1970s has survived? Also, does anyone archive Viewdata pages? Viewdata was not a broadcasting technology but provided pages with a compatible display format to teletext which pages could be accessed over a telephone line connection. William Overington 31 July 2002
