Use the Keyboard preference tool to configure the keyboard accessibility options. To open the Keyboard preference tool, choose System → Preferences → Keyboard. Select the Accessibility tab to display the accessibility options.
The Accessibility tabbed section provides the following options:
Allow to turn accessibility features on and off from the keyboard (Alt+A) – Determines whether keyboard accessibility functions can be turned on or off with a key command.
Simulate simultaneous keypress (Alt+S) – Allows multiple shift (or other) keys to be entered individually but processed as a single combination keystroke. This keyboard accessibility technique is known as “sticky keys”.
Disable sticky keys if two keys are pressed together (Alt+B) – Automatically exits the sticky keys mode if any key combination is being pressed normally (that is, at the same time instead of pressed individually).
Only accept long keypress (Alt+O) – In this mode, keys must be pressed for a given length of time before they are accepted as input. This accessibility technique is also known as “slow keys”. This portion of the Accessibility tabbed section also supplies a delay slider (Alt+D) to indicate the press-down delay before the key is accepted as input.
Ignore fast duplicate keypress (Alt+I) – In this mode, successive entry of the same key will only have a single instance of that key accepted as input. This accessibility technique is also known as “bounce keys”. This portion of the Accessibility tabbed section also supplies a delay slider (Alt+E) to indicate the press-down delay before successive keys are ignored.