"Entacards" as they are affectionately known are used by the University of Cambridge Computer Laboratory to control access to open the doors of its various rooms and labs. They are manufactured by Chubb, which is a british company. Mine has a picture of me and a barcode. It also carries my CRSID and the issue date.
At the bottom is an opaque black strip which is actually partially transparent in infra-red. The barcode is replicated in the strip and read by the readers on the doors.
Legend has it that in the new computer lab building, we won't use them any more and there will be radio tags to open the doors. I say: "Long live the Entacard"
PS: the name is a cunning pun "Enter"-"card" = "Entacard", get it??