Ceefax / Fastext Question

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PitfallJones
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Ceefax / Fastext Question

Postby PitfallJones » Wed Nov 23, 2011 1:26 pm

So when did TVs and Ceefax/Teletext start using the four coloured buttons to link to other pages?

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I've read that Fastext was added with the addition of extra information in lines 24 and 27 with FLOF - full level one features
which also included black text on a coloured background (I don't think the Beeb can do this) but can find no mention of the date of introduction anywhere - late 80s maybe? I guess FLOF was added prior to Teletext level 1.5 - which the UK never used.

http://www.topteletext.com/topteletext/new_projects_teletext.asp

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jgharston
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Re: Ceefax / Fastext Question

Postby jgharston » Thu Nov 24, 2011 11:24 am

It was before 1985 because I remember using it at school, and with the ATS Teletext terminal. Somewhere I've got the Telesoftware download that detailed this sort of information.

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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PitfallJones
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Re: Ceefax / Fastext Question

Postby PitfallJones » Sat Nov 26, 2011 12:24 pm

Thanks for that - it's amazing what Google can reveal once you know what magic words to type. (In this case 'ATS Teletext terminal').

The Teletext System User Guide (June 1983) mentions row 27 chain linked pages but goes no further so the theory of linked pages must have been around before is was actually used by the BBC and ITV.

Where as the Advanced Teletext System User Guide (1986) fully covers the four coloured links and even assigns them to function keys. It has a picture for a Ceefax page from I believe Sun 20 Apr 1986 - which is the earliest Ceefax picture I have discovered anywhere on the net that displays links. I noticed even in this page the idea of using words for links hadn't occurred yet.

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I also came upon an advert for some teletext tvs in 1983 that clearly don't have coloured buttons on their remotes.

http://www.80sactual.com/2008/09/some-1980s-television-sets.html


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Ideally I could narrow it down by tracing back old TV model numbers and seeing what teletext support they had - but I haven't had much luck finding any yet.

Anyway this all fits in nicely with your experience of a date around 1985.

Thanks again.

- PJ

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PitfallJones
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Re: Ceefax / Fastext Question

Postby PitfallJones » Fri Apr 28, 2017 3:06 pm

Seems it was a little later - Oracle started in Jan 1987 !

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Coeus
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Re: Ceefax / Fastext Question

Postby Coeus » Fri Apr 28, 2017 6:12 pm

Does anyone know how this relates in time to the introduction of page caches?

As originally implemented teletext sets would only have the RAM for the page being displayed so when you typed the number of a new page the set had to wait for it to be broadcast. Pages that were used more often were included more than once in the set of pages being broadcast.

My memory of this fasttext feature was on a set that did have a page cache which would enter the pages corresponding to the four colours into the cache even while waiting for you to press the button so when you did choose the page would appear instantly. What I don't know is whether the use of the coloured buttons drove the introduction of a page cache or whether it was something happenning separately that happenned to be well suited to this.

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Re: Ceefax / Fastext Question

Postby BigEd » Fri Apr 28, 2017 6:16 pm

I think the two ideas came together under the banner of FLOF - full level 1 features. That would be an uprated spec for new TVs which could then command a premium.

It seems the teletext page had room for 6 numeric linked pages but only 4 coloured labels. Any ideas how they were used?

I think I had at least one receiver which cached the next few sequential pages as well as (or possibly instead of) the four linked pages.

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Re: Ceefax / Fastext Question

Postby 1024MAK » Fri Apr 28, 2017 6:20 pm

I think it depended on the TV set. Memory for five pages was the minimum for fastext (currently displayed page plus either the four highlighted coloured links or with some sets, four user selectable pages).
Apparently later TV sets could capture more pages, so you could type in the page number, and if it was already in memory it would be displayed immediately. I had a Teletext decoder card for my PC that did this.

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RobC
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Re: Ceefax / Fastext Question

Postby RobC » Fri Apr 28, 2017 6:22 pm

Coeus wrote:What I don't know is whether the use of the coloured buttons drove the introduction of a page cache or whether it was something happenning separately that happenned to be well suited to this.

As a kid, I had a teletext TV that didn't have Fastext but would cache any four pages you chose by pressing a "remember" key and then entering the page numbers. You could then instantly access these pages by pressing the appropriate "recall" key. This was before I'd seen or heard of Fastext so I suspect predated it.

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Re: Ceefax / Fastext Question

Postby Coeus » Fri Apr 28, 2017 6:22 pm

There were pages that formed a set, i.e. page 1 of 4 (displayed 1/4). Again, as originally implemented, there were four version of the page in the broadcast set and you had to use STOP if you wanted to avoid the set automatically moving to the next one when it came around. I think with a page cache, again the set would cache all four and you could move between them with buttons but I don't remember exactly how.

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Re: Ceefax / Fastext Question

Postby Coeus » Fri Apr 28, 2017 6:26 pm

RobC wrote:
Coeus wrote:What I don't know is whether the use of the coloured buttons drove the introduction of a page cache or whether it was something happenning separately that happenned to be well suited to this.

As a kid, I had a teletext TV that didn't have Fastext but would cache any four pages you chose by pressing a "remember" key and then entering the page numbers. You could then instantly access these pages by pressing the appropriate "recall" key. This was before I'd seen or heard of Fastext so I suspect predated it.


The fact that it was four pages, though, suggests that maybe fasttext was in the process of being standardised and a manufacter of teletexts chips had already produced a chipset with a four page cache but as some of the other details weren't finalised sets couldn't yet to proper fasttext.

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Re: Ceefax / Fastext Question

Postby guesser » Sun Apr 30, 2017 4:30 pm

BigEd wrote:It seems the teletext page had room for 6 numeric linked pages but only 4 coloured labels. Any ideas how they were used?


Links 0-3 are the red, green, yellow, cyan links, Link 5 is used as an index page link usually to link back to the index for that section of the service (tv remotes usually have something like a page with an 'i' in it). Link 4 has no defined use but "may be used for additional automatic page acquisition". I've never seen it used for anything in the BBC, ITV, and Channel 4 data captures I have. They all set that link to page 8FF (a null link).

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Re: Ceefax / Fastext Question

Postby guesser » Sun Apr 30, 2017 4:35 pm

Coeus wrote:There were pages that formed a set, i.e. page 1 of 4 (displayed 1/4). Again, as originally implemented, there were four version of the page in the broadcast set and you had to use STOP if you wanted to avoid the set automatically moving to the next one when it came around. I think with a page cache, again the set would cache all four and you could move between them with buttons but I don't remember exactly how.


Modern TVs have such an enormous amount of memory available compared to 70/80s technology that they can pretty much cache an entire teletext service. Several of the manufacturers' implementations display an additional line of subpage codes in row 25 on carousel pages and use left and right cursor keys to navigate through them.

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Re: Ceefax / Fastext Question

Postby BigEd » Sun Apr 30, 2017 4:36 pm

Thanks!


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