The RS-485 is a serial bus standard. It is an evolution of the RS-422 and like it, the RS-485 cable is composed of a twisted pair. We can form a point to point network linking up to 64 devices (32 transmitters and 32 receivers, this is the diference with the RS-422), and up to 1200 meters in length. It operates in differential mode on levels -6V and +6V and can reach speeds up to 10 Mbits/s. It can operate in half-duplex or full duplex with 4 wires.