RS422 is resistant to the communication bus used mainly in industrial installations or in environments with requirements for high noise immunity.
RS422 (also known as four-wire RS485) using four-wires, known as Rx+, Rx-, Tx+ and Tx-. The line is duplex, meaning that one device on the line at one point may transmit and receive data. RS422 is suitable for transfer as a direct replacement for most uses RS232.
The maximum length of one branch is RS422 up to 1200 meters. It can be extended by using repeaters. On one arm may be according to a maximum of 32 devices. Equipment must not be linking to the so-called stars (from all devices into one point), but gradually from one to another. As a jumper wire should be used twisted wire - ideal as using two twisted pairs of normal cable for computer network (TP cable).
