Joker perhaps has device for opening doors (5,4)
I believe the answer is:
smart card
But I can't explain it at all! Could you help me understand?
(Other definitions for smart card that I've seen before include "used to carry out financial transactions" , "financial authorisation" , "Piece of plastic with micro-processor" , "piece of plastic that stores data" , "ID with microprocessor built in" .)