Cable Selection

Low capacitance, shielded twisted pair cable is recommended, particularly for installations where the RS-485 cable length is expected to exceed 1500 feet. The part numbers in the first column of the table below are specifically designed for RS-485 applications. The cables, such as Spectracom part number CW04xxx (where xxx equals the length in feet), have a braided copper shield, nominal impedance of 120 ohms, and a capacitance of 12 to 16 picofarads per foot. For cable runs less than 1500 feet, a lower-cost twisted pair cable may be used such as those listed in the right column.