Kempston Micro Electronics
The Kempston Joystick was a ground breaking and oft-imitated joystick that enjoyed huge success during the mid 1980s. It consisted of a square base, two large red buttons (for left or right handed use) and a black pommel stick. It used the Atari_VCS standard D-subminiature connector and was primary designed to work with the ZX Spectrum Kempston joystick interface but also with the compatible ports built into other home computers such as the Amstrad CPC, Commodore 64 (& Vic-20) and later Commodore Amiga and Atari ST.
Internally the joystick used a series of metal contacts to signal movement to the computer. When the user applied pressure to one side of the stick it caused the two contacts to touch and form a circuit. This was a primitive design compared to later micro-switch based joysticks, but it meant that it was extremely reliable. Faults could usually be repaired by unscrewing the base and adjusting the metal contacts so they touched correctly.
It attracted its fair share of imitators on 8-bit computers who copied the colour scheme (itself somewhat derived from the original Atari joystick), but also more brazen copies which used yellow, square buttons or microswitches but essentially the same pommel design.
The design has been honoured most recently by the Commodore 64 DTV 30 in 1 device which fits an entire Commodore 64 and 30 games into the shell of a Kempston look-a-like case which runs off batteries.
Kempston Joystick Interface
The Kempston Joystick Interface was a 3rd party expansion for the Sinclair ZX Spectrum which enabled a joystick to be connected to the machine. The interface was extremely popular and was a defacto standard for the platform.