On Jun 14, 21:54, Jules Richardson wrote:
> On Mon, 2004-06-14 at 21:40, Carsten Brasholt wrote:
> > Hi again,
> >
> > I just opened it up....
> > It's got 5 chips inside it.
> > 74LS00
> > 74LS74
> > 8251AP-5
> > 74LS32
> > 4060
> >
> > Does this help??
> >
> > I know that prestel is some sort of teletext service - and perhaps
a
> > dial-up service, but this unit doesn't really look like it's
related to
> > a modem.....
<pedant>
Strictly speaking, "teletext" is broadcast, the generic term is
"viewdata" :-)
</pedant>
> The 8251 is a serial comms chip - looks like you have an Amstrad
> cartridge giving you a serial port on the DIN plug, to which you'd
> connect up a serial modem in order to access Prestel.
>
> I have a feeling Prestel was 1200 baud downstream and 75 baud
upstream,
> but someone else will know for sure :-)
Correct. The idea was to make most use of bandwidth with the
technology of the early 1980s. Most of the data went from a central
host to a terminal; what went back was mostly typed (page numbers, data
entry fields, email), and few people regularly exceed 7 cps. There
were special ports running normal symmetric 1200 half duplex and full
duplex for "Information Providers" on a machine called Duke, but
ordinary users didn't have access to Duke, or those ports. Data
available included train and airline timetables, news, weather, lots of
microcomputer stuff including "telesoftware", and all sorts of other
things.
There were quite a few other viewdata services besides Prestel. Some
large businesses used viewdata, a few bulletin boards did, the Open
University, some banks, and it was widely used by travel agents --
there was a special system run by a consortium for clearing holiday
bookings. Derivatives included the French Minitel service, Germany's
Bildschirmtext, and Canada had something too. The last commercial
viewdata system I know of (Bank of Scotland HOBS service) finally
closed last month (though it may still be running for special
purposes).
It would seem that there is little point in finishing off the rough
edges on my X-Windows Prestel terminal software ;-)
--
Pete Peter Turnbull
Network Manager
University of York
Received on Mon Jun 14 2004 - 20:53:43 BST