The Compact Box serves as a fieldbus station with a wide variety of I/O functions – without expansion options. The Coupler Box can be extended via the Extension Box modules. Communication takes place via IP-Link. IP-Link is an optical fiber communications connection with a data transfer rate of 2 Mbit/s which is capable of transmitting 1000 items of binary I/O data in approx. 1 ms, rapidly and securely. Smaller configurations are correspondingly faster. Because of the high usable data rate, the IP-Link coupling does not reduce the performance of the fieldbus at all. The Coupler Box collects the I/O data and corresponds in terms of its function to the Bus Coupler from the Beckhoff Bus Terminal system.