Input and Controls:

1. Allow connection, substitution, or addition of alternative input devices (that is, keyboards, pointing devices, and so on)
2. Make all controls operable from keyboard
3. Have all controls mounted on the front of the device (that is, facing the user)
4. Use push buttons primarily
5. Use concave buttons (especially where sustained force is required)
6. Avoid twisting motions (instead, use push buttons or edge controls)
7. Minimize force required for operation (that is, less than 2 Newtons)
8. Make all controls operable with one hand (preferably with one finger or assistive pointing device)
9. Make controls tactually discernible