Here is a problem attributed to mechanical constraints. On a high density router, such as a SMPTE SDI router, the input BNC connectors are aligned due to access and having enough room to connect and disconnect the cables. The EQ tends to be placed close to the connector for return loss (a SMPTE specification) thus the lines from the input to the back of the card can become long. If the design is modular, there is typically a backplane and central routing card in the system. The trace length, via, connectors, large (long) backplane vias and traces all come into play. The TDR (impedance plot) shows how the Zo changes with distance as the path runs. Thus, on critical networks, one needs to think about the transmission line model and the resulting losses. A solution to this is a small crosspoint part to not only give the required functionality, but to also provide the signal conditioning to connect the end points at the required rates and reach. Signal conditioning is needed at 3 Gbps in most systems, and also in some 1.5 Gbps systems depending upon reach. This graphic illustrates the loss via a TDR plot of the signal path. The trace, connector, and vias all have a hand in the losses that need to be corrected for.