From: William Overington (
Date: Wed Jul 31 2002 - 06:00:18 EDT

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.

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

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