Terminating Resistors-An Overview

Terminating resistors are used in communication cables to prevent reflection of the transmitted signal.  The reflected signal can cause interference which may affect data transmission.  Hence, to prevent this resistances are connected in parallel.

The value of the impedance will match the wave impedance of the line.  Thus a communication line with an impedance of 120 ohms will have a 120 ohm resistor connected across it.  Short cables can function without terminating resistors.