Wikipedia
The Taito NESYS (Network Entry System) is an arcade game network communication system by Taito Corporation. It connects up arcade machines via a network, and allows players to participate in national rankings and online play, as well as allowing arcade operators to download updates for games. The Taito NESiCAxLive uses the Taito NESYS system to allow online distribution of games.
The system uses the NESYS IC Card smart card to allow players to save game data at arcade machines. These cards will remain compatible with the machine even as the games it hosts change. The card itself can hold data for multiple different games at the same time. This is similar to the Konami e-AMUSEMENT system, and the smart card function of the SEGA ALL.Net system..