Software House iSTAR Pro 4U - Page 17

Components/Connections
17
If you want to use RM 8 or RM 16, set S1 position 1 to OFF (No Termination) on
that ACM. See Figure 8.
NOTE
The total length of the half duplex RS-485 connection is 4000 feet.
FIGURE 8. RM Terminations
S1-1=ON
S1-1=OFF