How do I register my SmarTrip card? You can also fax a note with the SmarTrip® card serial number, your name, address, and email address to 202-962-1035 or mail the same information to: SmarTrip Regional Customer Service Center PO Box 220568 Chantilly, VA 20153. Your smart card is fitted into a thin horizontal slot behind the MY SKY cover on the front of your box. Remove the smart card and on the back it contains a number beginning with 0000, 01 or 02 followed by 8 digits.
One of the feature I use the most is SSH authentication to access multiple servers. But I cannot use the second one after having used the first both of the smart cards ( not simultaneously) on the same computer.