BeebMaster - Acorn Teletext Adapter




Acorn
Teletext
Adapter






I bought this from E-Bay towards the end of April 2003 and it is one of the best things I have ever bought.

It was advertised as having no connector at the end of the ribbon cable but I had soon fixed this with a new 34-way connector and a metal saucepan used to apply even pressure to the connector to crimp the blades onto the ribbon cable.


The adapter comes in the standard Acorn "cheese wedge" box.


At the back is an aerial socket and four red wheels for tuning in the four main channels. No such thing as channel five in 1983!!



At first I tried a portable aerial but no luck so I moved to the outside aerial. The Teletext Filing System has an option to detect the reception so you select the channel with one of the function keys, select the detection option and play with the wheels until you get a bar showing a good signal strength and the teletext header information appears on the top line of the display.

Once everything is tuned in, select your channel, type in the page number and read away or save the pages to disc for future reference.

Pages of teletext take up only 1K of disc space because they are mode 7 images so this means you can fit 399 pages of teletext onto a double-sided DFS disc!

In fact, this would not be possible due to the catalogue limitations under DFS unless you were to cobble all the pages together into a much larger files. Using a dual catalogue system you could get 61 or 62 pages on either side of a DFS disc.

Under ADFS, you could fit 622 pages of teletext on a Large disc. This is because each directory can only hold 47 entries. You would need 13 subdirectories inside the root directory to take all the pages. Each subdirectory uses up five disc sectors so thirteen would need 65 sectors. A further seven sectors are lost to the root directory and free space map making a total of 72 sectors. A large ADFS disc has 2,560 sectors leaving 2,488 free to hold teletext pages. Each page of teletext is exactly 1024 bytes or 4 sectors meaning there is room for exactly 622 pages of teletext on a Large ADFS disc. All the subdirectories would have 47 entries and the root directory would have to take 11 pages of teletext and the 13 subdirectories.

In the 1980s and until part-way through the 1990s (I think) software could be downloaded from Teletext as well as the pages themselves. This was known as Telesoft. The BBC broadcast special pages of Teletext in the 700 page range where programmes could be captured for use on the BBC micro.

Since June 2003, the Teletext Adapter has been permanently connected to Station 1 via the 1 MHz bus out socket on my Technomatic Winchester. It lives by the side of the Technomatic in my glass-fronted cupboard.

One of the nice features about the 1 MHz bus interface is that it allows several devices to be connected at once in a chain. The Teletext Adapter was given the status of last device by Acorn meaning that it lives at the end of the chain of add-ons and has no 1 MHz out socket. If I want to connect anything else to the 1 MHz Bus of Station 1, it will either have to go before the Technomatic or between the Technomatic and the Teletext Adapter.



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