Moxa Technologies CP-132U - Manual (Page 79)

Connection Cables and Cables Wiring
CP-132U Series User’s Manual 5-7
Impedance Matching and Termination Resistors
When using RS-422/485 serial communications, an electrical signal that travels through
two different resistance junctions in a transmission line will sometimes give rise to signal
reflection due to the impedance mismatch. Signal reflection causes signal distortion, which
in turn contributes to communication errors. The solution to this problem is to establish the
same impedance at the ends of the transmission line, as in the line itself, by terminating the
ends of the line with resistors.