HP-65 more on the card reader

[albertofenini]

Hi Tony,
look at this picture,
the bottom (usually curved) should be common to all
the inner or shorter (the middle one) is the first activated since is the first encountered by the card and I believe turns on the motor
If this is true, then the upper one (A in my picture) should the one the is triggered by the upper left corner of the card.
What are B and C doing ?
And, how can I check if a recordable card is treated like a record protected ?
Thanks for help !