ICP DAS USA I-7531-FD User Manual page 11

On the other hand, the I-7531-FD module has built-in two 120Ω terminating
resistors, and the user can use the jumper to select whether to enable it. Among
them, JP1 is used to adjust the terminal resistance of CAN port 1, and JP2 is
used to adjust the terminal resistance of CAN port 2. If the user wants to adjust
the terminal resistance, who needs to open the casing of I-7531-FD, and will
see the positions of JP1 and JP2 as shown in the figure below:
The following connection statuses present the condition if the terminal
resistor is enabled (default) or disabled.
Figure8. Adjustment of Terminator Resistor
I-7531-FD CAN Repeater User Manual (ver. 1.0, 2021/10/21) ------11
Figure7. JP1 and JP2 positions
Disable
(Deactivate)
Enable
(Activate)