Rick's b.log - entry 2018/08/15

Minitel 1B

For those who don't know what Minitel is, think Prestel. Or videotex. Only it was wildly popular in France, to the point where adoption of the Internet was initially slow in France because people preferred (and trusted) Minitel. When I first came over here to France, it was quite common to see adverts quoting a four digit phone number, like "3634". Minitel progressively expanded to include colour and graphics primitives, however like Prestel it used the videotex style 1200/75 data transfer rate.

Its origins are an experimental project in Brittany in 1978 that was rolled out to the rest of France in 1982, to become the largest and most popular pre-internet online service.
Around the turn of the century, France Telecom estimated that there were 25 million users of Minitel (out of a population of around 60 million), and about ten thousand companies provided twenty five thousand different services - all accessible through the little Minitel terminal. As with Prestel, some services were free and some were paid. The range included messaging services, directory enquiries (always free), adult services, plane/train booking, and mail order companies. In 1998, Minitel generated revenues of €832,000,000, of which €521,000,000 (yes, half a billion euros) was channelled to the many service providers. This was 1998. When reasonably fast (33k6 (56k would arrive in 1999)) dial-up with local rate phone numbers was available. Minitel was finally switched off in 2012, which was big news here in France.

The service is correctly called "Télétel". "Minitel" is the name of the terminal, and it actually has a meaning other than the diminutive size of the terminals - Médium interactif par numérisation d'information téléphonique.
The service operated at V.23 which means it is a half-duplex data transfer that receives data at 1200 baud and sends it at 75 baud. Being half-duplex, data only flows in one direction at a time. This is contemporary with similar systems such as Prestel, but it's somewhat extraordinary that users in the early 2010s had the patience...
The terminal is entirely passive. That is to say that it is a screen and a keyboard and little else. A very small amount of firmware decodes the input data or display and encodes the keyboard for transmission. There is no storage and precious little memory. There is a method of printing the screen (to compatible serial printers), but that's it. The remote system does all of the work, the Minitel just acts as the human interface end.

On the back of my Minitel is the specification plate. Interestingly there is an embossed version underneath, with this metal plate placed on top. The end of guarantee, 1988/30 refers to week 30. In other words, the week of 25th July. When the movie Cocktail with Tom Cruise was popular. The first Die Hard movie was released ten days prior, and it's the week Tandy announced the 1000SL computer (an IBM clone running an 8086 at 8MHz, one of many of their "1000" PC clones). I know my model was built in the beginning of January 1986 (from arkings on one of the boards inside). That would be a couple of weeks before the terminal mission of Space Shuttle Challenger. Popular in music was "West End Girls" by the Pet Shop Girls. Sometimes you're better off dead, there's a gun in your hand, it's pointing at your head, you think you're mad too unstable, kicking in chairs and knocking down tables, in a restaurant in a West end town, call the police there's a mad man around, running down underground, to a dive bar in a West end town...
Sorry. In case it wasn't blatantly obvious (uh, all over this blog), I grew up in the '80s so all this is the stuff of my childhood memories.

The interesting thing here is he description of the two modes. Mode 1 is CEPT Videotex at a text resolution of 40×25. Again, not unlike Prestel or Teletext (including the block graphics). Mode 2 is more interesting. It's a plain ASCII (ISO 2022/6429) terminal at a resolution of 80×25.

I think it would be rather amusing to debug software on my Pi using a thirty two year old Minitel! Unfortunately it will probably be a while because the Minitel's serial port is "weird" which means that an adapter board needs to be built that uses transistors to switch according to the serial data. One cannot simply plug in an RS232 cable.

The Minitel was ridiculously easy to open. Two clips under the handle, and two underneath. Flip them, then the back would normally slide off. It's a little harder in reality because there's a clip-in mains filter board (with fuses) that needs to be dealt with first to release the mains and telephony cables.
Once inside, the machine is laid out pretty clearly:

An interesting thing about the video/power board, asides from the big wire patch to the transformer, is that many of the test points and all of the adjustment points are named, actually built into the board design.

Now for the control board. There's no overall image as I have not stripped the machine, and there's plenty of dust as I didn't want to touch the circuitry any more than was absolutely necessary. Anyway, here are the three most important ICs:

The final chip in the photo is a D4168C 8KiB "XRAM" (an SRAM with improvements) hat acts as the memory and screen buffer for the EF9345.

Other ICs on the board are TIC MODEM (HC3 5731-R) and TIC FCC (M04 8801?). All I can say that you can still by the modem chip from China, and searching for anything with "FCC" in the title is going to end up being something to do with the American FCC...
There are also various logic gates and such, much as expected. Somewhere there will be a V.23 modulator/demodulator. This may well be the function of the TIC MODEM.
There doesn't appear to be any hardware for DTMF tone generation, so it may dial by loop disconnect using the on-hook relay. I would say that such a thing isn't going to stand a hope of working with VoIP phone lines, but then one isn't going to get far trying to push an analogue data signal down a compressed stream.

Not pictured is one 5V voltage regulator with a heatsink. At a rough guess, this will be stepping down the 8V from the video/power board to the 5V used by the rest of the motherboard. Being built in the '80s, it will be 5V TTL logic levels.

Now here's something new. I've seen Minitels before. I've seen inside Minitels before. I haven't seen this before...

The keyboard is a membrane matrix. Nothing unusual about the electronics. In terms of keys, there are three primary sections. The alphabetic keys (like a regular keyboard), the numeric keys (like a phone - with 123 at the top), and special function keys: Connexion/Fin, Fnct, Sommaire, Annulation, Retour, Répétition, Guide, Correction, Suite, and Envoi.
The keyboard is not terribly pleasant to use. Marginally better than the Oric-1. About the same as a graphical calculator. It is laid out in AZERTY format (this is France), with extreme eccentricity regarding the accented characters typical in French. Ctrl-Répétition will get you the œ ligature (which I think is only used in a handful of words), Ctrl-Retour gets it uppercase. Ctrl-Suite gives you the ß which isn't even French (unless France loved Betamax?). Ctrl-Correction would give you a lower case C with cedilla. God help you if you wanted an accented 'e' (any type). I think Ctrl-number gave some other stuff, but there's no indication on the keyboard. And when in American mode? Different characters... no French.

Reassembly was simple. Just put the back cover back on, clip into place, and refit the filter board.

David Pilling's Hearsay 2 has a Minitel emulation, with source as Main.c.vxterm. Pop over to David's site for the software/source.

Your comments:

Please note that while I check this page every so often, I am not able to control what users write; therefore I disclaim all liability for unpleasant and/or infringing and/or defamatory material. Undesired content will be removed as soon as it is noticed. By leaving a comment, you agree not to post material that is illegal or in bad taste, and you should be aware that the time and your IP address are both recorded, should it be necessary to find out who you are. Oh, and don't bother trying to inline HTML. I'm not that stupid! ☺ ADDING COMMENTS DOES NOT WORK IF READING TRANSLATED VERSIONS.
 
You can now follow comment additions with the comment RSS feed. This is distinct from the b.log RSS feed, so you can subscribe to one or both as you wish.

David Pilling, 17th August 2018, 16:06

Is there a Minitel legacy, some place on the web where one can connect to a Minitel source, can't believe they chucked the lot. After BT pulled the plug on Prestel/Micronet, some people carried on with private systems - Silicon Village. Anyway if there is, you'll be able to test your terminal, and... compare it with the Hearsay emulation. We never had any complaints, but realistically it can't have been perfect because testing time was very limited and some of the subtleties of French pages were going to escape us. Oddly way back then, no one had test suites, "see if your terminal will pass these tests".

David Pilling, 17th August 2018, 16:11

Well, yes: https://medium.com/@cq94/get-your-minitels-back-the-computel-vid eotex-bbs-is-back-1d8c42f1ea17    Doesn't seem much else.    I suppose I could say "hey is all the Micronet stuff archived somewhere" - also chucked.

Rick, 18th August 2018, 21:39

I've been looking at the standard (the "stum1b" file) and the terminal is definitively VT100 - the codes are described in part 3, chapter 2, section 4 (around page 170).    Whereas we might call it "VT100 terminal emulation", the French call it "Le standard téléinformatique"...

Rick, 18th August 2018, 21:44

David - looks like somebody built a Minitel server with a homebrew modem (!) and a Pi. https://www.jelora.fr/post/2017/08/27/Serveur-Minitel.html    Sorry. I cannot test. Not only do I not have an analogue modem any more (well, I lie, I have my original 14k4 Courier but the power pack is long gone), I also do not have a phone line capable of handling data. It's a virtual landline coming out of the Livebox. VoIP and SIP...    (so I can't test the real Minitel either)

David Pilling, 24th August 2018, 01:37

I suppose VT100 begat ANSI, which was a standard. As ISTR we had dealings about this, for Hearsay I tacked colour codes onto VT <whatever>. Pre-internet I could not pull the ANSI spec. out of the air. Why they not do Minitel over telnet like Arcade.

Rick, 8th September 2018, 07:20

Small correction: the Minitel 1B doesn't dial. At all. You enter the number using a normal phone and when you hear squeaking you press the Connexion button on the Minitel and hang up the phone...  [I think Minitel 2 is the first one that supports dialing by itself]

marcel ohanian, 22nd March 2021, 03:38

i just currious new device price or not

Rick, 22nd March 2021, 19:22

I think these were given away by France Telecom because the paid services were quite expensive so they probably expected people to use such services.  Also, if you had a Minitel, you no longer got phone books (because you can freely use your terminal to look up addresses).    No idea how much they cost new, if for example you wanted to upgrade to a better model? Looking on Google just gets me a hundred thousand terminals on eBay...

Peter Renaud, 31st March 2021, 02:09

I recently acquired a NIB Minitel Telic for Canada. It has an 8052. Do you have the 2764 EPROM contents? I am thinking of replacing the 8052 by an 8752 with RS232 set for 8N1.

Rick, 1st April 2021, 14:41

Sorry, I have not copied the ROM.  My EPROM programmer worked with my Acorn A5000 and I've not switched that on in two decades. Don't know if it still works...

Add a comment (v0.11) [help?] . . . try the comment feed!
		Your name
		Your email	(optional)
		Validation	Are you real? Please type 91518 backwards.
		Your comment