Resistors R6 and R3 are 0-Ω resistors. The input terminals (IN+ and IN-) have corresponding sense lines so that the inputs to the device can be terminated on the lines with 50-Ω to an oscilloscope. This allows the input signals to be observed with minimal loading and distortion. There are also optional input resistors R4 and R5 for direct 50-Ω terminations if required by the input signal generator, otherwise they can be left uninstalled.

Additionally, the pads from R4 and R5 can be used to solder a 100-Ω termination resistor for LVDS input signals.