RS485 is resistant to the communication bus used mainly in industrial installations or in environments with requirements for high noise immunity.
RS485 (also known as two-wire RS485) uses only two wires, A and B, also known as RxTx+ RxTx- and more positive or more negative wire and cable. The line is half duplex, meaning that at one point, it can transmit only one side (the system of request - response).
The maximum length of one branch is RS485 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 - Using their knowl perfect example of a twisted pair cable for the current computer network (TP cable).