To access the underground:

To recharge your card/pass:

(Seen in Paris last week)

Why do I blog this? I just wanted to point the size and color of the contact area (coherence and homogeneity). This big violet circle is intriguing and as you can see on the second picture there is a sort of "tail" maybe to facilitate the passing of the card/pass when moving. The tail allow the user not to stop to validate his/her card.