Line Termination - Advantech ADAM 4000 Series User Manual

E
Appendix
E. 2 Line Termination
Each discontinuity in impedance causes reflections and distortion.
When an impedance discontinuity occurs in the transmission line the
immediate effect is signal reflection. This will lead to signal distortion.
Specially at line ends this mismatch causes problems. To eliminate this
discontinuity terminate the line with a resistor.
Figure E-4 Signal Distortion
The value of the resistor should be a close as possible to the characteristic
impedance of the line. Although receiver devices add some resistance to
the whole of the transmission line, normally it is sufficient to the resistor
impedance should equal the characteristic impedance of the line.
Appendix E RS-485 Network E-5