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Shelton Instruments were the people behind the original design of the Nascom 1. They were based in London.

Sig-Net was a totally new concept, whereby a series of boards - processor, interface, memory, etc. - were interconnected by flexible wires.

Each board had its own power supply and many variations of computer could be evolved from the basic system components.

The Sig-Net 200 series computer had a number of these modules housed in an enclosure that can have two integral floppy disc drives. The system came with 64 KB of RAM and up to 4 KB of ROM. There were two RS232 interfaces and a 4-channel real-time clock.A hard disk controller could be connected on-board.

The system was indefinitely expandable, even to a multi-processor system, using Sig-Net modules. CP/M 2.2 operating system came with the computer allowing the vast CP/M library of software to be used.

Please consider donating your old computer / videogame system to or one of our partners from anywhere in the world (Europe, America, Asia, etc.).


I own a Shelton Signet 200 cabinet, with twin floppy disk drives built-in and a separate monitor.

I am trying to find out if anyone has a copy of CP/M, or other software for this machine please?

Best wishes, Ross

Monday 26th October 2020
Ross Milbourne (United Kingdom)

I used to build the signets. I started working with Chris Shelton in 1981 building the signet3 systems and was the main person doing customer support. It was very sad to see the end of the signet in 1994. I was the only one from the early years still supporting the product. I ended up buying all the stock, some 300 units in various forms and provided support to the various end users still using the Signet3 multiuser systems. I would love to hear from any one who might have spoken to me.

Friday 17th April 2020
Jayesh Shah (london)

I spent many years programming and selling Shelton Sig-net they were designed by a guy called Chris Shelton of Shelton Instruments and they had CPM operating system. I used to program in Microsoft Compiled Basic and the biggest system I sold was a 48 user to Sunseeker Travel in Huddersfield in 1988. Originally it was one processor per screen all connected to a hard disk using sheltons purpose designed ringring system which was a bus between the processors and the z80 running the hard disk. Rhodime made in scotland in 7/14/21 megabytes that formated down to 5/10/15 MB. I have lots more information if your interested.

Sunday 1st July 2018
gary smith (United Kingdon)


NAME  Sig-Net
MANUFACTURER  Shelton Instruments
TYPE  Professional Computer
ORIGIN  United Kingdom
YEAR  1981
KEYBOARD  Depending on the video terminal used
CPU  Z80-A (or B)
RAM  64 KB to 128 KB (one-processor system)
GRAPHIC MODES  A graphic card was available - Features unknown
SOUND  Beeper
SIZE / WEIGHT  Unknown
I/O PORTS  2 x Serial RS232, 1 x Parallel Centronics
BUILT IN MEDIA  1 to 4 200, 400 or 800 KB 5'' floppy disc drives
POWER SUPPLY  Built-in power supply unit + one power supply per card
PERIPHERALS  Optional 7 MB hard disk (£3300 + £600 for the controller)
PRICE  Basic version (200/2) about $2900 + video terminal

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