Date   : Mon, 18 Jul 1994 13:16:11 +0100
From   : Jon Kale <spbcajk@...>
Subject: Re: Teletext graphics question...

>> Anyone know for sure what the hold and release graphics teletext controls
>> do ?
>> 
>> Also, there's a "conceal" display, which I assumes makes all characters
>> from that position onwards appear blank, but how is it turned off ?
>> 
>> James.
>
>VDU 6 or pressing ^F.
>
>I think VDU 21 makes it go into conceal mode.  You can't type ^U to
>do this because ^U is intercepted as line erased.

The VDU21/VDU6 is used to switch the display on/off; the 'conceal display'
character is a teletext code (implemented by the Mullard I/C) which allows
for effects such as the 'InVision' cricket scores (try this out if you've
got a teletext TV - it's really handy!) To switch it off, just use a text
or graphics control character (ie CHR$128 to CHR$135 or CHR$154 to CHR$161)
and then the rest of the string. Hold and release graphics I never quite
sussed; I think they're to do with getting several control chars mapped into
the same space (tho' I don't have a clue how - don't quote me. I'll go home
and find out and post tomorrow.)

                                Cheers
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                                                             spbcajk@...