/Vintage/Sinclair/82/Peripherals/VTX 5000 Modem (Prism Microproducts)/

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Prism Microproducts - VTX 5000 Modem

Blurb from the AD, Manual and Reviews

[misc. sources, collected by Ciproducts]

The Prism VTX5000 modem is one of the most ingenious add-ons in the world of home computing. By linking the most successful home computer, the Sinclair Spectrum, to Prestel's Micronet and similar databases, it has opened the way for thousands of micro owners to step into the exciting field of communications.

The Prestel database struggled to find users from the day it first went 'on-line'. Prestel 'sets' were expensive, and the amount of information available on the database was too limited to offer much of an advantage over an ordinary newspaper. However, with a suitable modem and software, most home micros can access Prestel. And so, in order to exploit this possibility, Prism formed Micronet, a separate area within Prestel dedicated to news and information about micros. Modems and software that enabled access to Micronet and Prestel were soon made available by Prism, and the project proved immensely successful. The number of users and the range of information services available continues to grow.

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.

If you tire of Prestel, you can always try to communicate with other Spectrum users. The VTX5000 is also designed to link two Spectrum computers via the telephone lines, so they can send messages and programs directly to each other. The speed of transmission is a healthy 1200 baud. Early versions of the modem were sold without the software to do this, but now a tape that facilitates this data transfer is included. Obviously, this software is of use only to Spectrum owners who have friends who also have Spectrums and VTX5000 modems.

Several other communication standards are in common use for modems, but the VTX5000 cannot cope with them. The most important limitation is the modems lack of the standard needed for the many free bulletin boards, which are being set up by enthusiasts around the world. These operate at a data rate of 300 baud, but the VTX5000 can't transmit as slowly as this.

Anyone who really wants to explore the whole area of computer communications with their Spectrum may find it more suitable to buy an RS232 interface (particularly Sinclair's own ZX Interface 1) and use a general purpose modem. However, this would probably entail writing your own software, wiring cables and so on. The VTX5000 is ideal for those who want to use Prestel only.


Name Letzte Änderung Länge 
Current Selling Prices/ 2019-08-20 05:25 10 
XL/ 2019-08-20 05:25
box - front.jpg
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