"Difficult to use parking ticket machine"

The parking ticket machines used by Pinderfields Hospital in Wakefield and Pontefract General Infirmary are difficult to use and have no clear instructions. They require you to enter your registration number using multifunction buttons which act as number and letter buttons at the same time. To switch between 'modes' you press a coloured button, the only way to discover this is trial and error and you have to press it again to switch back from numbers to letters or vice versa. For all the user knows they could be required to hold the button in like you do on a computer keyboard. Not only is this like a puzzle, but also requires a degree of manual dexterity. Baring in mind that there must be many elderly people wishing to park at a hospital the complexity of this technology is misplaced.

I have a Masters Degree in Computer Science and researched Human Computer Interfaces, yet still found the ticket machine a mystery!