If you think you've seen it all before, then take a closer look at the Sig/Net

This is the first known advert for Chris Shelton's Sig/Net, the range of hardware which is considered as perhaps the first ever modular multi-user personal computer system[source: https://www.theregister.com/2013/08/21/unsung_heroes_dr_chris_shelton/?page=1].

With its budget monochrome design with a single spot colour, the advert came from Shelton Instruments of Copenhagen Street in London, a company founded in the early 1970s. 

By the time of the advert, Chris Shelton was already well-known as the designer of the [#Nascom 1], as well as for his earlier work with microcontrollers and microprocessors. 

The more conventional arrangement for multiple users at the time was to share a central micro - including its CPU, memory and disks - via a number of serial ports, each connected to a terminal.

As more users were added, performance generally got worse as all users were sharing everything.

With Sig/Net, this idea was modified so that users had their own CPU and RAM "module", but the modules were all connected over a flexible 26-way "port bus" to a base module with hard-disk storage, printers, and so on.

There was a downside to this arrangement - these interconnect cables could only be up to a metre long, however each satellite supported up to three connected terminals, and these could run over RS-232 at much longer distances.

The components of the satellite units were also modular, however a basic set up - CPU and RAM, a floppy disk controller, twin serial connections and two power supplies, one for the CPU and one for the floppies - retailed for £1,299, which is about [[1299|1981]] in [[now]].

However that didn't include the cost of the terminals or - apparently - the actual floppy disk drives.