Viewdata Adaptor/Terminal

[Dave Moll]

I wasn't quite sure where to place this thread, as Viewdata sits somewhere between computing and telecomms. Although I plumped for computers, I would be entirely happy if it were considered more appropriate in telecomms.

Having now taken possession of the terminal in this thread, I have had a first go at trying it out. After powering up and following the instructions...



... to press "C", I get the following:



and pressing "#" clears the screen. Sometimes, however, I get the following screen on startup and pressing "C" has no effect:



As it arrived with a comms lead without the usual Plug 505, I am left trying to fathom out which wire is which. The five wires are coloured red, white, blue, green and orange, though the latter appears to be unused as it is absent at the equipment end.

Any tips with this would be appreciated, as I can't really progress further until I make a successful connection to a telephone line.

[Graham G3ZVT]

I've not seen a Viewdata terminal like that before.
Viewdata was a generic term for these 1200/75 baud systems, as was Videotex in some parts of the world, but I haven't heard of Teleview in a UK context. A Google search seems to point to it being a Singaporean term, in much the same way as Prestel was a Post Office brand.

If I'm right and it did come from Singapore, maybe it never had a plug 505 attached?

Does it carry the familiar BEAT green circle approval sticker?

[TonyDuell]

Starting at the plug body the conventional order of the wires on a Plug 505 is :
Green
White
Blue
Orange
Red

For Viewdata, green and red go to a normally closed relay contact in the terminal unit, this opens to disconnect the normal telephone when you're using viewdata. White and blue are the line wires to the modem. Orange is, indeed, not used.

Diagram N4410 shows the wiring of the Jack 96 (to take Plug 505) for Viewdata applications and may be useful. I've attached the reverse-engineered schematic of the line interface board in one of my Viewdata terminals which might help too.

[Dave Moll]

Originally Posted by Graham G3ZVT

Does it carry the familiar BEAT green circle approval sticker?

No BABT green circle, nor red triangle for that matter.

Originally Posted by TonyDuell

Starting at the plug body the conventional order of the wires on a Plug 505 is :
Green
White
Blue
Orange
Red

Thanks. That will indeed come in useful if I manage to source a plug 505 and the terminals aren't colour-coded.

Originally Posted by TonyDuell

For Viewdata, green and red go to a normally closed relay contact in the terminal unit, this opens to disconnect the normal telephone when you're using viewdata. White and blue are the line wires to the modem. Orange is, indeed, not used.

Great stuff! That has moved me a little forward in that, with blue and white connected to the line, when I press "#" after "C" I get a brief burst of dial tone. I'm puzzled, however, that this only lasts for a brief period and doesn't then permit me to dial out.

Originally Posted by TonyDuell

Diagram N4410 shows the wiring of the Jack 96 (to take Plug 505) for Viewdata applications and may be useful. I've attached the reverse-engineered schematic of the line interface board in one of my Viewdata terminals which might help too.

Thanks. Yes, I already have a Jack 96A wired up according to N4410 - to which someone (possibly yourself) pointed me in an earlier thread

[Graham G3ZVT]

Originally Posted by Dave Moll

Great stuff! That has moved me a little forward in that, with blue and white connected to the line, when I press "#" after "C" I get a brief burst of dial tone. I'm puzzled, however, that this only lasts for a brief period and doesn't then permit me to dial out.

I would not expect to be able to dial out manually with the keypad on the unit.
The telephone number(s) were usually pre-programmed.
This is implied by the flow-chart "Press 1" on your unit. I would expect that digits 2 to 0 are also available for programming. The same NV RAM that holds the telephone number(s) also typically held a 10 digit user number associated with each phone number. to be sent on the 75 Bd back-channel. Perhaps because of the ease you could access someone else's account, the end-user was not given details of how to reprogram them. Also, NV RAM of the time was often quite (er) volatile, so I would expect the contents to be corrupt by now.

You could of course cheat and use a parallel DTMF phone to dial the service.

I'm sure I read recently that there are various test numbers for Viewdata emulators available on the PSTN, maybe they are Micronet 800 related. Someone will know.

[Dave Moll]

Originally Posted by Graham G3ZVT

I would not expect to be able to dial out manually with the keypad on the unit.
The telephone number(s) were usually pre-programmed.
This is implied by the flow-chart "Press 1" on your unit. I would expect that digits 2 to 0 are also available for programming. The same NV RAM that holds the telephone number(s) also typically held a 10 digit user number associated with each phone number.

Yes, I did wonder about that

Originally Posted by Graham G3ZVT

Perhaps because of the ease [with which] you could access someone else's account, the end-user was not given details of how to reprogram them. Also, NV RAM of the time was often quite (er) volatile, so I would expect the contents to be corrupt by now.

You could of course cheat and use a parallel DTMF phone to dial the service.

I'm sure I read recently that there are various test numbers for Viewdata emulators available on the PSTN, maybe they are Micronet 800 related. Someone will know.

In the circumstances, the parallel telephone sounds like the way to proceed. My intention is to access Telstar.

Edit: the likelihood of tracking down instructions to reprogram the (non-)volatile RAM being on a par with tracking down unicorn droppings.

[Dave Moll]

Well, that was an interesting exercise...

1) I dial the number on the parallel telephone and receive the expected modem sounds

2) I press the "#" key on the viewdata terminal and the sound is briefly duplicated from the terminal before being silenced on both this and the telephone

3) A stream of characters appears on the screen, some of which make sense but many of which are garbage.

[Dave Moll]

Originally Posted by Dave Moll

A stream of characters appears on the screen, some of which make sense but many of which are garbage.

Having tried again but connected direct to the landline rather than via my PBX seems to have eliminated most of the garble and I get the Telstar welcome screen as shown below. Unfortunately, there is no response to pressing keys on the keypad of the adaptor (such as the requested press of # to continue).

[Philips210]

This thread brings back memories of my limited experience with Viewdata terminals. Around 1986, I purchased a complete Prestel unit from Sendz Components which was intended to be connected to a modified 16" ITT TV receiver fitted with the CVC40 chassis. The Prestel unit was also made by ITT or STC and dated from around 1979/80. The telephone numbers were stored in a ER1400 EAROM IC. The last time I used the system was sometime in 1987. It was fairly expensive to use as it was based on line connection time so you were constantly aware about the mounting usage costs, a little like the days of dial up before broadband became the norm.
I regret dismantling it for parts but at least some of it was put to use in later projects.

Regards,
Symon

[ortek_service]

I got a NOS? Teletext board from Sendz for £5? in the mid-80's, but not sure if it was for any particular TV (may have been something like a VM6100? - but no internet back then and Prestel didn't have that sort of info on it!).

Although at least Prestel was only a local call, so call-charges were only 1p/min in the evenings etc. However, a subscription to Prestel cost rather more, so very few had accounts (I think I just used a 'Guest' demo one, back then). And it was via a Beeb etc. computer, as I never saw an actual Pretel-equipped TV being used (When my Dad bought a new Philips G11, he was only persuaded to get the Teletext, rather than the much-rarer Viewdata version).

Although I think I may now have a Sony Viewdata, and I've seen one of those small Minitel? terminals (that were used in France for their version of Prestel etc.) being sold quite cheap at Radio Rallies. I do have one of those quite-chunky Tandata integrated-keyboard units, that plug into a TV and also a Tandata IR Keyboard for a different one (but no base unit!), I got as surplus (from Greenweld?).

The Sendz Telextext board I got was quite large (nearly A4-paper size) and a rather-vintage design, with lots of not too common Texas Instruments IC's - luckily all socketed, and I too ended-up stripping the board - mostly for all the nice Wima boxed-polyester decouplers and the IC sockets, as I hadn't got many at the time. I may still have the board, and should have the TMS9980? CPU, TMS2716? EPROM and TMS4014? RAM's IC's.

But I doubt it's now worth restoring back to original, with no analogue TV transmissions to get Teletext from (But maybe someone's produced a low-cost generator, like 625-to-405 line converters, that could insert the data into the right TV lines to allow telextext adaptors etc to be shown working again, using a BBC-Computer / PC etc to create teletext pages for it.

[winston_1]

Originally Posted by ortek_service

But I doubt it's now worth restoring back to original, with no analogue TV transmissions to get Teletext from (But maybe someone's produced a low-cost generator, like 625-to-405 line converters, that could insert the data into the right TV lines to allow telextext adaptors etc to be shown working again, using a BBC-Computer / PC etc to create teletext pages for it.

All you need is a cheap satellite receiver on Astra 19˚W with a composite output. Most German and Italian channels still carry teletext.

[electronicskip]

Its good to see another member interested in Prestel related equipment,i was beginning to think there was only one or two of us .
Here is few pictures of some of my Prestel units including a Tantel prestel adaptor and my Sony Viewdata Prestel terminal kindly given to me a few years ago by another forum member.

Apologies for the poor pictures, a mix of cheap mobile phone camera ,me and reflections .

[circuitryboy]

I believe I was buying the same - TI-9980 - boards from Sendz.
Looking at their adverts on WorldRadioHistory, it was a "Texas Viewdata Decoder VDP 12/80 Issue 3 with all IC's" (but a lot of vacant sockets).
For the princely price of £10. (I must have felt richer back then.)
I bought several. The boards stripped easily and those TI sockets were good quality.
I've got the 2716 listing somewhere and I did tinker one board to run some LEDs.

[ortek_service]

Yes, thanks for the PCB-photo - It was the same one I'd got (I recall it being supplied in foam-padding folded-cardboard, with mine having red Wima boxed polyester capacitors. I must have stripped virtually everything else off it, including 0.1" SIL headers, resistor networks, and 74 TTTL IC's etc, to recycle on projects. And found the TI IC sockets were easiest to remove, by pulling tops off and removing the contacts individually, then re-inserting these into the socket tops.
I think mine was also missing many (optional RAM etc?) IC's

And I now see it was actually advertised as a Viewdata Panel, which I later also remembered was actually priced at £10.
(I doubt I'd now pay more than a pound or so for these, from what similar old boards are priced, at many Radio-rallies)

Although Sendz were always a bit disorganised, and you could sometimes see the same item listed more than once, at different prices, and I never got an itemised receipt (Someone told me, that if you just sent them a Postal Order for a reasonable amount, you'd still get everything you asked for even if advertised prices came to rather-more than the amount you'd sent!).
I never went there in-person, but someone who had told me it was a very-large (Aircraft hanger?) warehouse place.
I've still got many of the resistors etc. from their surplus mixed-components bags of bandolier strips etc.

I must dig out all the remnants of mine, to see if any of the other TI TMS... IC's may be useful for restoring / building some vintage prjoects with.

[ortek_service]

Originally Posted by winston_1

All you need is a cheap satellite receiver on Astra 19˚W with a composite output. Most German and Italian channels still carry teletext.

Thanks for the info - I presumed Analogue Terrestrial transmissions had now ended across Europe / much of the World, and I hadn't thought there might still be some working satellites transmitting these (As I thought Astra Digital transmissions had replaced the original 'Analogue' ones).
Although I presume their Teletext won't be in English, so might need to brush-up on my German / learn some Italian!

[ortek_service]

Co-incidentally, I've just found a few Viewdata articles, mentioning some of the systems & costs + that of MODEM's (I never realised the Post Office rented these out, for a rather high cost!), whilst looking through some PCW magazines of the early 80's - See attached extract
(I also spotted in the May'80 issue, a review of an unusual American Altos_ACS8000-2 SBC by someone who became one of my Uni Lecturers 9 yrs later. And I'd never known they'd written for PCW, although they did write a Modula-2 programming book most of us found we needed to buy!)

[cmjones01]

You can also generate and send teletext using a Raspberry Pi and a bit of software: https://www.raspberrypi.com/news/cre...etext-service/

I tried it a few years ago and it works well. I got pages showing on the Acorn Teletext adapter connected to a BBC Micro.

Chris

[circuitryboy]

Having handled that TI Viewdata panel for the first time in (30?) years I just had to dig for info I'd not found BITD!
It's likely that Prestel/Viewdata enthusiasts et al. know of this, but I have just discovered:-
www.blunham.com/Radar/Teletext/index.html
So now I know something of the enigmatic TMS3529 and TX012. And a lot more.
There's a .png of Iss.2 of that board with 2 more ICs fitted.
And if all the information there is not enough, you can pass into a "Carlsbad Caverns" of Radar.

[ortek_service]

Thanks for that link. I think I may have stumbled across something similar a while ago, but it was quite useful to read. Where it seems to indicate that these products weren't too successful, with all the design issues they had!
Maybe that's why there were quite a few unused surplus ones sold, if they gave up on it and it never really got fitted into many TV's

Although I don't know there were ever many Viewdata-built-in (Early 'Smart' ?) TV's - I only know about the Philips G11, and suspect they had their own PCB design for that (Like the more common Teletext-only with their SAA-5xxx chipset board version).
There was an SAA-5070? 'LUCY' IC, intended for viewdata use - I have a couple of Torch Computers boards (for the Beeb?) that just had this on them, So I suspect Philips would have used that.

I'm not sure if all Viewdata boards also supported Teletext as well, or if two boards were required in the TVs.

[tony brady]

Thorn also made a prestel/ viewdata set in a version of the 9600 or 9800, I can't remember which now but should still have the service manual.

I found the trio of boards that were fitted in our stores at Thorn Newhaven. these boards were using the SAA series but were not made by Thorns. I suspect they were made by Mullards/ Philips. they were glass fibre double sided and roughly 20x20cm

one board did the teletext which was the bit I was interested in as I was making teletext decoders for my friend and I.

another board was for connection to the telephone line and I presume the 3rd board was for the viewdata part. I threw these 2 boards out long ago but still have the decoder