E-Amusement
9th Style was the first version of IIDX to have support for Konami's new e-Amusement system, which can be used for the saving of stats and records to "entry cards". The entry cards were magnetic cards usually containing game artwork, inserted into a card reader mounted on the sides of the cabinet, and protected by a 4-digit pin. The cards could save stats and scores in between games, allowing new features such as the ability to sort songs by a player's previous performance on it (by letter grades, clear status, or full combos). When connected to the internet, scores could also be uploaded to the internet, but unlike future implementations, this was entirely optional. 9th Style did not require a network connection for full e-Amusement compatibility, and thus could be used while offline too. 10th Style however, would require a network connection to use e-Amusement.
Read more about this topic: Beatmania IIDX 9th Style