Dialing A BBS With A Spectrum 48k

Prestel & ViewData Services

In the UK back before the internet arrived there was a system called Prestel that provided various online facilities via a ViewData interface. This was similar to the Minitel system used in France and was closely related to Teletext.

Here is my Minitel terminal all setup to test my dial in gateway and connect to Level 29 BBS.

And here it is logged into Level 29 BBS. Notice the screen size is very restrictive due to the 40 column width compared to most ASCII terminals that have 80.

Micronet 800

As part of the Prestel service large customers could rent pages (known as frames) or the Prestel mainframe could hand off to an external system to provide other services.

One of the most popular services was Micronet 800, it provided chat rooms, multiplayer online games and message boards about various topics.
It was called Micronet 800 due to that being the entry page number provided by Prestel (you entered 800 to get to the main page within Prestel). 

The main problem with connecting to Micronet / Prestel was that you needed a modem, most home users of the time didn't own a machine with a serial port so in an attempt to get more users Micronet provided a package for the Spectrum. As the Spectrum 48k did not come with a serial port and couldn't display the resolutions required to show the ViewData frames this was a problem. Micronet got round this by providing a modem with built in ROM and hardware to update the Spectrum so that it could use the service.

The modem sits nicely under the Spectrum and connected to the bus at the back.

Modem Functions

When you connect the unit to the Spectrum it patches the ROM to load the Micronet code.
This gives you get a nice splash screen when the machine is turned on.

When pressing a key you are returned to the main system menu.

There is a mode for automatically logging onto the service (this remembers your ID number and enters it at the relevant prompt).
You can save frames, store programs and check the mailbox. The system also allows you to drop back out to Basic so that you can use the Spectrum without having to disconnect the unit.

Selecting log on asks for you ID and then gives you this screen.

At this point you have to manually dial the number to connect the modem.
When you hear the tone you flick the switch on the front of the unit to go online.

Problems Connecting

As the unit is designed to connect to a ViewData system at V23 (1200, 75) it does not have the modern modem facilities such as auto-bauding. It expects the other end to be the same. When trying to connect to Level 29 BBS we hit the problem as the modem on the other end is using Bell protocols and we are using the European CITT ones. The main difference being the tone frequencies that they use.

My modern modem has an AT command to switch modes but will usually just figure out the other ends requirements.

As we don't have that option I altered my ViewData system dial in gateway to connect to Level 29 via telnet. This allows me to dial my machine locally and the software then connects to the BBS via telnet does any character translation required and passes the data back to the Micronet modem.

Connected To Level 29 Via The Gateway

When I used this in my office it worked fine, I could type my user name (with a little bit of effort as the keyboard is a bit awkward on the Spectrum) but my monitor wouldn't keep the sync with the Spectrums video output and the image kept rolling. I then moved this downstairs on a very long telephone extension so that I could use the TV.
I think that something was getting messed up as the keyboard was not sending the correct key presses back to the gateway.

Anyway you can see the main login page that we are connected to. The Minitel terminal in the office works perfectly with this so I think I need to sort a shorter telephone extension cable out and try it again.

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