I had one of these once. The Acorn Electron was the little brother of the BBC Micro.

Photo Album:

It was a nice little machine, despite its weaknesses - slower processor, only one sound channel and no Mode 7 (Teletext) graphics. It was a great little machine, but it did suffer from production problems - a lot seemed to go wonky. I got through a few before I gave up and got my money back. I was able to get a BBC Micro with the refund a bit of extra saving.

This particular model came my way several years later, and it has the two official Acorn expansion boxes bolted on. The large L shaped one is a Plus 3 - a 3.5" floppy disk drive, which gave the Electron Acorn’s ADFS, as well as much faster loading times. This, dear reader, is the time when most software was loaded off tape, and it took ages.

The box at the back is the Plus 1. This gave toy the joystick port (actually, it did more than joysticks, being an analogue input port), and a printer interface. At the top are two cartridge slots. You could buy games and other software which loaded from them. The aim was to store the software in a form which could be run straight from the cartridge, but it seemed to be the practice to treat it as another filing system and load games into the main memory. There were other add ons which plugged into these slots, including a floppy drive from a third party, and if memory serves me correctly, a teletext system.

You can see from the photos that the Plus 1 & Plus 3 connected via edge connectors to the Electron, and are held in place by some pretty hefty screws.

There was never a Plus 2. I wonder what it would have been.