@paco

Each iteration of the keyboards had its own set of patents, I presume. There was probably A patent, which started the ball rolling. I remember walking through some of the tech halls with the patents engraved on plaques.

As other responders pointed out the keys were like Braille.

I like your UI takes. I started out in s/w and UI design for Nortel. We built one of the first (if not the first) commercially available Voice mail. The subtly of the number pads for directions, and my favourite, prompts for beginners, intermediate and expert users was fun.

We had fun messing with people.
We would have our prompt read out the usual 10 digit phrasing (3-3-4) in pairs (2-2-2-2-2)

Try it next time you give a phone number! They will glitch.

Not 212-555-1212 but 21-25-55-12-12!