In this article the termination is described and when it's needed.
What is “termination” and do I really need it?
Yes, you need it when using RS422 or RS485. Although most things will work without any termination for short distances, it is needed in the field installation. Typically this termination consists of a 120 ohm resistor, between the two data lines, at the two far ends of the line, to avoid reflections. If the termination is not installed properly, the typical result is that the data is corrupted. This results in that it seems like the node is not responding properly.