StandardsInternational : Manufacturer specification
In typical office environments today there are often mixed network installations consisting of 10 Mbps Ethernet, 100 Mbps Fast Ethernet or 1000 Mbps Gigabit Ethernet systems. The system rack is perfect for those installations for inserting a maximum of 21 different converter shelves (e.g. 2x 100 Mbps and 1x 10 Mbps). Dual channel shelves are available for Ethernet and also for Fast Ethernet.