Game Console Controller - Dismantled for reference and curiosity
When the Sony PlayStation was released in December of 1994 the original controllers featured only a segmented directional pad, four action buttons, four shoulder buttons, a 'Start' and a 'Select' button.
To accommodate flight simulators (and like games) in 1996 Sony released a double stick joystick controller called the 'PlayStation Analog Joystick' that looks nothing like the original controller and more like someone had strapped two Wingman joysticks to a board. The joystick controller made use of potentiometer based tech to capture subtle movements in a full joystick range of positions rather than relying on directionally placed digital switches.
With the influx of games that would support the use of analog sticks, both flight based and otherwise and the fact that the PlayStation Analog Joystick was never going to sell enough units to make it worth developers creating games that support it Sony released the 'PlayStation Dual Analog' controller.
The Dual Analog Controller is much the same physically as the original controller with the addition of two analog joystick/thumbsticks at the bottom. These made use of the same technology refined for use with the PlayStation Analog Joysticks. The thumbsticks also added two additional buttons to the controller beneath the thumbsticks, inside the pad that when pushed into the controller activated the switches.
The Japanese release of the Dual Analog controller came with vibration feedback motors installed but due to design problems the motors were not installed in versions released in other countries. If you dismantle a non-Japanese Dual Analog controller it's a simple matter to install your own motors and the circuitry and motor mounts are already there.
In 1998 Sony again revamped the controller and released the 'PlayStation Dual Shock' controller. The Dual Shock incorporates all of the digital and analog features from the original and Dual Analog controllers and adds a now properly working set of vibration feedback 'rumble motors'.
The Dual Shock controller became exceptionally popular with gamers and developers who could make use of the features and is the most sold PlayStation controllers to date .
It is worth nothing that there are numerous more subtle changes to the controllers such as differing shapes of the bumper buttons, slightly different length casings, indents on the thumbsticks on the Dual Analog, etc. however for the most part and at a glance they all looked essentially the same bar the added features and are all unmistakably PlayStation controllers.