Contemporary Control Systems BASrouterLX Installation Guide - Manual (Page 11)

TD120100-0IC
11
After removing the router cover, three jumpers are accessible on a 6-pin jumper
block located near the EIA-485 connector. These impart 604 Ω of bias via the upper
jumper (pull-up) and the lower jumper (pull-down), and 130 Ω of termination
impedance with the middle jumper. With all three jumpers in place, the effective
termination resistance is 120 Ω — consistent with the MS/TP standard. If the
router is not installed at the end of a segment, remove all the jumpers and install
120 Ω at each far end of the bus.
Figure 10 — Internal Termination and Bias