These cards are used in the Digital SAT TV decoders.
The silvercard.gif attached to the post of the user
Darkman is the schematic inside the card.
The clock comes from the Digital SAT TV decoder
when the card is inserted in the card slot.

You need a Smart Card when the TV program is
encrypted. The EEprom is used to store the keys.

Example:
http://www.francoelettronica.it/ISO_7816.htm

Luciano