price: 60 GBP platforms: ZX81
Adds colour, SCART interface for sharp RGB picture, joystick and RS232 ports, ROM expansion socket.
It also provides 16 RAM pack, 8k of RAM to allow user-definable characters, two colour modes, load / save sounds, Quicksilva emulation, reset button, expansion bus throughput.
The two colour modes both offer 15 colours. The first provides a Spectrum-like attribute file giving ink and paper colours to each character. This mode requires game-makers to support it. The other mode provides a lookup table to map colours to the character spaces, which allows colours to be mapped to existing games.
Find out more / buy at: http://www.fruitcake.plus.com/Sinclair/ZX81/Chroma/ChromaInterface.htm