Moxa Technologies DE-211 - Manual (Page 22)

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NOTE: When setting up a multidrop network, a daisy-chained network should
be used. Construct your device-to-device wiring as indicated in the
above figure.
Enabling a Termination Resistor
For RS-422/485 serial communications, when an electrical signal travels through
two different resistance junctions in a transmission line, the impedance mismatch
will sometimes cause signal reflection. Signal reflection causes signal distortion,
which in turn will contribute to communication errors. The solution to this problem
is to establish the same impedance at the line ends as in the line itself, by
terminating them with resistors.
The impedance of the termination resistor should equal the characteristic impedance
of the transmission line. The resistors should be added near the receiving side.