Today I Received...

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Derek_Stewart
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Re: Today I Received...

Postby Derek_Stewart » Sat Apr 20, 2019 8:54 am

Hi,

You could be mistaken, see the description on World Of Spectrum:

https://www.worldofspectrum.org/hardware/feat24.html

[quote="World Of Spectrum]
In producing an add-on to connect the Sinclair Spectrum to Micronet, Prism came up against a big challenge, as the machine is unsuitable for this application. It has no RS232 or serial interface, which means that ordinary modems cannot be connected. It has a screen display of 32 columns by 24 lines, and Prestel requires 40 by 24 display, as well as the complicated 'teletext' graphics system. The company produced an all-in-one unit designed specifically for this single task; the Prism VTX5000 modem.

The unit contains all the interfacing needed to connect the Spectrum, a direct-connect 1200/75 baud modem and software to access Prestel. This not only provides the standard functions for logging into the system, but also uses the Spectrum's graphics screen to imitate a true 40 by 24 teletext display. As a result, for £100, Spectrum owners can buy all the hardware necessary to join Micronet.

The VTX5000 sits underneath the Spectrum and connects to its expansion connector. The ribbon cable between the two has a third socket so that other spectrum peripherals, such as a printer or Microdrives, can be connected. This unit plugs directly into the phone system rather than using an acoustic coupler (in which the telephone handset is pushed into two rubber cups on the modem). This provides much more reliable communication.
[/quote]

I had one of these rubbish VTX 5000 units, it connected to the Spectrum expansion port.


Regards,

Derek
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Dave
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Re: Today I Received...

Postby Dave » Sat Apr 20, 2019 11:14 am

I’m quite sure I am not mistaken. I owned and used the thing for 12 years. It came with a gray case and they sent me a hex tool and black case and metal plates to swap it so it matched my QL. They also sent me an updated ROM because the first ROM had an awful bug that stopped most of the Hayes commands from working.

It was advertised in the QL magazines too, but low profile.


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Dave
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Re: Today I Received...

Postby Dave » Sat Apr 20, 2019 11:21 am

It looked almost identical to this, but had the VTX5000 logo, and a switch that had three positions... 1200/75, 300 and 1200bis.

http://www.beebmaster.co.uk/8bitadd/Prism4.html

The same guy designed the Tandata stack that designed the Prism modems. From Cumbria. Nice guy.


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Re: Today I Received...

Postby RWAP » Sat Apr 20, 2019 7:28 pm

I never owned a modem - but are you mixing it up with the Astracom modem - https://qlwiki.qlforum.co.uk/doku.php?i ... com_modems or possiby the Bright Star modem - https://qlwiki.qlforum.co.uk/doku.php?i ... star_modem


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Dave
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Re: Today I Received...

Postby Dave » Sat Apr 20, 2019 11:42 pm

The Astracom was somewhat similar, yes. The other modem, no. I did have an Astracom modem - the exact one shown - for a few weeks for a review and it was nicer than the Prism modem I had. Unfortunately, it was expensive and I had to return it at the end of the review period.

The Prism modem I bought came as standard with a gray case, not a black one, and I got a custom black one from the manufacturer. The front and back where hand cut, so they may have made them from what they had laying around. Like I mentioned, the one I had was a very early unit that required firmware upgrades to even work properly.

I also had one of the very first USRobotics HST modems in 1987? It got destroyed by lightning in 1989 or 1990. I just googled it and they still sell a model in the exact same style, but supports 56K - I think mine topped out at 9,600 HST.


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Dave
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Re: Today I Received...

Postby Dave » Sat Apr 20, 2019 11:47 pm

One thing I'm very sure of: the VTX5000 had screws in the bottom, and the Astracom had screws in the corners of the front and back plate. Both used hex screws. I had them both at the same time and one was sat on the other. The Astracom was really nice and I'd be happy to own another. I'd get a phone line just to run a BBS again ;)


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janbredenbeek
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Re: Today I Received...

Postby janbredenbeek » Sun Apr 21, 2019 12:46 am

Dave wrote:I also had one of the very first USRobotics HST modems in 1987? It got destroyed by lightning in 1989 or 1990. I just googled it and they still sell a model in the exact same style, but supports 56K - I think mine topped out at 9,600 HST.

I bought my first USRobotics in 1990, this was a 14400 HST model. It was superseded in 1991 by another USRobotics 14400 HST/V.32bis (which also supported V.23, which pleased many QL owners :) ). And finally in 1994 a V.everything which supported up to 33600 - the 56K upgrade offer came somewhere in 1996 but by then I had already upgraded to ISDN which supported 64K (or 128K with two channels bundled) so for me 56K was more or less obsolete. I still have that modem by the way and a ZyXEL U-1496E+ so I could play around a bit with BBS software :) .
These modems were not used with the QL though - the speeds were already too fast for the crappy serial ports and Hermes came around only in 1992 long after I moved the BBS to PC hardware. SER3 couldn't handle it either since it used the BAUDX4 signal from the 8302, and because of the internal prescaler in the 6850 the maximum was 4800 baud!

Jan.


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Dave
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Re: Today I Received...

Postby Dave » Sun Apr 21, 2019 6:31 am

I’m working at editing the 6850 driver I believe you wrote to work with a 68681-similar device. It’s tough going but I am making progress.

I don’t suppose you have a commented copy of it? :D


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janbredenbeek
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Re: Today I Received...

Postby janbredenbeek » Sun Apr 21, 2019 11:30 pm

Dave wrote:I’m working at editing the 6850 driver I believe you wrote to work with a 68681-similar device. It’s tough going but I am making progress.

I don’t suppose you have a commented copy of it? :D

I don't know which version you have, but I believe the source on GitHub is reasonably well commented?
https://github.com/janbredenbeek/QL/blo ... M/ser3.asm

Jan.


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Dave
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Re: Today I Received...

Postby Dave » Mon Apr 22, 2019 12:56 am

Most excellent. Thank you for the pointer!

It's just a matter of knowing where to look, and I never do!



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