In offline mode the SH4 can work as a standalone device that holds an internal database of cards and users.
You just need the Ethernet port to setup the unit and the device will follow the access rules without the need for LAN connection.
In online mode the device is connected with a server running the HWg-DCD software. This server manages all the access rules.
The relevant part of the entire user database is loaded in each SH4 so that you can still access your technology even if your network connectivity fails.