There are two sets of terminals on the Xenta Repeater that are labeled identically.
Vista Lon Network
The duplicate power supply and communications terminals are internally connected.
The power supply and communication connections can be made either to the upper or the lower terminals as they are internally connected. The extra set of terminals is strictly for convenience purposes.
One segment of the Lon network should be connected to the COM1 terminals and the other segment should be connected to the COM2 terminals. The only other wiring required is to connect the Xenta Repeater to a 24V power supply.
Wiring Example #1
This is the most traditional wiring schematic used with a Xenta repeater. Segment #1 comes into COM1 and is the end-of-line for a bus topology. A terminator is placed at the repeater. Segment #2 continues on out of COM2, and represents the beginning-of-line for the next segment, thus is also terminated at the repeater.
Wiring Example #2
This example is actually the same as Example #1, but is showing that the upper or lower terminals can be used for convenience, as they have electrical connectivity from top to bottom.
Wiring Example #3
Example #3 shows Segment 1 coming into COM1 on top and carrying on out of COM1 on bottom. This segment does not get terminated at the repeater because it is not the end of line for this segment. However, COM2 does represent the beginning-of-line for the second segment, and is therefore terminated at the repeater.
For more information on how the Xenta Repeater works see the following article: The Xenta Repeater provides signal restoration and conditioning on LON networks.