Sharing the Prestel Adapter or a Modem over Econet

[marrold]

Some of the Econet documentation mentions sharing Modems and Prestel access over an Econet. Admittedly I can't actually find where they're mentioned but I don't think I dreamt it.

Having read through the manual for the Prestel Adapter it says users can share it using the *REMOTE functionality, which was a bit of anti-climax, I was expecting something a bit more sophisticated.

Is anyone aware of any other options for sharing a Modem over Econet?

Cheers

[arg]

Lots of things were done, but I'm not aware of any commercial/supported product that precisely fits that description - though I know of several people doing ad-hoc demo/experimental/proof-of-concept remote modem servers, and there were probably lots more that I never heard of.

One thing that was supported and widely done was to run dial-in services (Communitel or similar software) which could hence export a Viewdata/Prestel pages over the modem to expose facilities available on the Econet. An extreme example of this was the Gnome At Home - a BBS with half a dozen BBCs each with a modem, communicating over Econet, not just the base set of pages stored on the Econet fileserver but various real-time user to user facilities between the dialled-in users.

For the dial-out modem server application the technology certainly existed: at SJ, we had the *FAST protocol (built for BBC terminals to control admin functions of our fileservers) that provided a reliable byte-stream protocol underneath the terminal layer, and that was entirely suitable to carry terminal traffic to a modem server. We built a demo one (I think using one of our Z80 machines as the modem server rather than a BBC, but with Econet BBCs as terminals to that). The protocol was standardised through the Econet Standards Group (becoming known as "streams"), and Torch were very interested in it, but I don't know whether they actually built any products out of it.

The problem (at least in the education market) with the idea of the modem server was that daytime phone charges were so high that a modem server that let stations on the Econet dial out willy-nilly wasn't actually a good thing to have. Usage of the phone line needed to be carefully supervised, so if you were going to do that you might as well just go to the one machine with the modem and use it directly. Even if you did countenance the idea of a modem server, it couldn't provide simultaneous service to more than one user - all the things you might connect to with a modem in those days were single-user dumb terminal style services (either Prestel/Viewdata or else 'teletype' style access to a minicomputer, things like Telcom Gold). So a modem server could in principle let one user at a time access the one modem + phone line, but that wasn't much use in a classroom situation. What people wanted out of a modem server was what they got out of a fileserver or print server: all the stations on the network able to use the resource at the same time. The DTI had a scheme to subsidise modems for schools, the "DTI modems in schools scheme", but it quickly became known as the "DTI modems in school cupboards scheme" as schools got their modems but couldn't find anything useful to do with them in the classroom setting.

That background led to another thing that also fits the "sharing a modem over Econet" category but isn't strictly a modem server: the Interspan email system. This provided local email between email client programs on Econet, with a modem-equipped server that would be left running overnight to answer the phone to a central server that moved email between sites. The mail send/receive programs and the mail/modem server all ran on BBCs (and used the DTI-supplied modems, which took a lot of work to make them work as there were two designs from different suppliers which both had major bugs in them!). The central server ran on an R140 plus PCs as modem concentrators.

[marrold]

Thanks for the detailed reply, that's some great insight

The DTI had a scheme to subsidise modems for schools, the "DTI modems in schools scheme", but it quickly became known as the "DTI modems in school cupboards scheme" as schools got their modems but couldn't find anything useful to do with them in the classroom setting.

Do you know what modems they were giving out, out of interest? Was it the Tandata Communitel one or something different?

That background led to another thing that also fits the "sharing a modem over Econet" category but isn't strictly a modem server: the Interspan email system

That sounds really interesting, is there any information on that floating around?

Cheers

[BigStu]

Thanks for the detailed reply, that's some great insight

The DTI had a scheme to subsidise modems for schools, the "DTI modems in schools scheme", but it quickly became known as the "DTI modems in school cupboards scheme" as schools got their modems but couldn't find anything useful to do with them in the classroom setting.

Do you know what modems they were giving out, out of interest? Was it the Tandata Communitel one or something different?

Tandata rings a bell, but can't remember the model. As I recall, there were two modems and one was a Dacom, possibly the 2123AD (if not that model a very similar looking one). Both had extremely buggy firmware (multiple versions) and poor compatibility in the command sets. A lot of effort was expended in producing a modem driver layer to hide all that and provide reliable end-to-end communications.

That background led to another thing that also fits the "sharing a modem over Econet" category but isn't strictly a modem server: the Interspan email system

That sounds really interesting, is there any information on that floating around?

I worked with ARG et al at SJ/Interspan (1985-1992) and then NET-TEL (1992-2000) after Interspan merged with them. I can probably fill in some of the detail on that if ARG doesn't (I believe I was the first person to write code on the Interspan project). My primary work was on Interspan, but with a lot of SJ related side projects along the way...

[flaxcottage]

Related but not an exact reply ... BITD we used to share an Acorn Teletext adapter throughout the school. Station 19 on the Econet physically hosted the Teletext adapter and ran a dedicated server. Users logged in with a library routine *TELETEXT. This logged them on to the Teletext server and ran a client that displayed the various pages.

One year we had live reporting of an England vs Pakistan cricket test match running untended during a computing lesson. Every so often someone would read out the scores etc. Sadly, Pakistan won.

[jgharston]

A teletext server was one of the first obvious shared resources after filing and printing, and was implemented early on and a common API was developed to locate resources: See https://mdfs.net/System/Teletext/

[arg]

This is the Tandata modem from the DTI Modems in Schools scheme.

Not sure why I kept this one: I liked the Dacom better at the time. The Dacom had bugs in its higher layer software (it had a pseudo-full-duplex mode that didn’t work properly), but at least the modem itself was solid and you could write your own duplex layer on top of that. The Tandata on the other hand had problems with the basic modem that were telephone-line specific, and if it didn’t work on your line you had to get an an EPROM to swap the internal firmware to fix it. I think the problem was lack of line equalisation giving asymmetric behaviour (zeros come out wider than ones or vice-versa) coupled with a software UART that was too crude to handle that.

Both were "smart" modems in the sense that the RS232 port to the host (BBC etc) communicated with software inside the unit rather than driving the actual modem directly.

[brianmartin_2001]

That modem and a few others from that era are about as rare as it gets.
Having experimented a good bit with the Communitel software (kindly supplied by John(Flaxcottage))
The Tm512 Communitel modem is highly sought after . The only other one
I know of is owned by DanielJ. I live in hope someone will revive a Communitel
host one day so I can dial into it. From what you said about the modem having line issues BITD
it's probably only gonna be worse now. Would love to see it happen though.