The document discusses InterLINK, a protocol that allows software applications to communicate with Eurogi hardware devices. InterLINK uses ASCII text strings sent over various communication channels like serial, Ethernet, and TCP/IP. Different firmware licenses offer access to different device resources and functions to applications. The InterLINK Server & Modbus Gateway license allows a device to act as a gateway between InterLINK and a Modbus RTU network, integrating other Modbus devices.