---
title: SHELTON INSTRUMENTS Sig-Net
categories:
- Computers
types:
- Professional Computer
origins:
- United Kingdom
years:
- '1981'
cpus:
- Z80-A
params:
  name: Sig-Net
  image: /media/museum/photos/shelton_signet_system_1.jpg
  company: /companies/shelton-instruments
  company_name: SHELTON INSTRUMENTS
  specs:
  - label: NAME
    value: Sig-Net
  - label: MANUFACTURER
    value: Shelton Instruments
  - label: TYPE
    value: Professional Computer
  - label: ORIGIN
    value: United Kingdom
  - label: YEAR
    value: '1981'
  - label: BUILT IN LANGUAGE
    value: None
  - label: KEYBOARD
    value: Depending on the video terminal used
  - label: CPU
    value: Z80-A (or B)
  - label: SPEED
    value: 4 MHz.
  - label: CO-PROCESSOR
    value: None
  - label: RAM
    value: 64 KB to 128 KB (one-processor system)
  - label: ROM
    value: 4 KB
  - label: GRAPHIC MODES
    value: A graphic card was available - Features unknown
  - label: SOUND
    value: Beeper
  - label: SIZE / WEIGHT
    value: Unknown
  - label: I/O PORTS
    value: 2 x Serial RS232, 1 x Parallel Centronics
  - label: BUILT IN MEDIA
    value: 1 to 4 200, 400 or 800 KB 5'' floppy disc drives
  - label: OS
    value: CP/M
  - label: POWER SUPPLY
    value: Built-in power supply unit + one power supply per card
  - label: PERIPHERALS
    value: Optional 7 MB hard disk (£3300 + £600 for the controller)
  - label: PRICE
    value: Basic version (200/2) about $2900 + video terminal
  forum_thread: 791
  oc_id: 810
  source:
    url: https://web.archive.org/web/20230528100258/http://www.old-computers.com/museum/computer.asp?c=810
    date: '2023-05-28'
---

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.