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same impedance at the line ends as in the line itself by terminating
them with resistors
Ideally, the two ends of the cable will have a termination resistor
connected across the two wires. Without termination resistors,
reflections of the fast driver edges can cause multiple data edges that
can cause data corruption. Termination resistors also reduce electrical
noise sensitivity due to the lower impedance, and bias resistors (120
ohms for twisted pairs) are required. The value of each termination
resistor should be equal to the cable impedance.
RS-422 or 4-Wire RS485 working model with termination resistor:
