I think its a better user experience to always show the number on a screen. Otherwise the user has to listen to the computerized voice recite the passcode, and

I think its a better user experience to always show the number on a screen. Otherwise the user has to listen to the computerized voice recite the passcode, and they have to memorize it before punching it in. This way, temporary memorization of passcode is avoided in both cases. The passcode is always rendered to pixels (computer screen or phone screen).