Analogue Personal Computer Joystick - Dismantled for reference and curiosity
The Tandy TRS-80 Joystick is a single fire/action button, analogue input peripheral primarily used for playing games on the Tandy Color Computer and Colour Computer 2.
The joystick connects to the computer using a round, five pin plug. The version designed for the Tandy Color Computer 3 has six pins to accommodate a second (black) fire/action button. As the joystick socket on all three computers had six holes the dual button version could be used on all three with the second fire button only functioning on the third.
Analogue joysticks use a continuous current through two potentiometers (pots) that varies as the user moves the stick. This allows for gradual increases in movement vs. digital joysticks having usually only four on / off switches for up, down, left and right; combinations of the four create diagonal input. Modern gaming thumb sticks are analogue vs. the digital D-Pad.
The joystick was intended to be self centring meaning when you release the stick it will find a middle location through the use of loaded springs and movement output would stop. Non-self centring joysticks just flop about. This centre is the dead spot where the software and computer hardware accepted that this level of current from each pot meant the joystick was in the middle so no action should be taken.
In reality this centre could be slightly off so there are two controls on the bottom of the joystick to allow users to set the centre.