ADLINK PCIe-7300A - Manual (Page 54)

44 Operation Theory
4.9 Active Terminator
For cPCI/PCI/PCIe-7300A, it is important to terminate your cable
properly to reduce or eliminate signal reflections in the cable. The
PCI/cPCI/PCIe-7300A support active terminator on board, you can
enable or disable the terminator by software selection.
The active terminator is the same as the one used in SCSI 2.
When the terminator is ON, it presents a terminal 110-ohm imped-
ance to the transmission line to match the line impedance. When it
is OFF, it just add a few pF capacitance to the line