RS232 to RS485 Cable Pinout - AllPinouts
interface converter electrically isolated RS485 communication interface to the PC serial port
EIA-485 cable usually made with twisted pair (like EIA-422) and may span up to 1200 metres. The recommended arrangement of the wires is as a connected series of point-to-point nodes, a line or bus. Ideally, the two ends of the cable will have a termination resistor connected across the two wires and two powered resistors to bias the lines apart when the lines are not being driven. The value of each termination resistor should be equal to the cable impedance (typically, 120 ohms for twisted pairs).