The RS-422 is a standard for serial bus. It is newer than the RS-232 and more efficient. The RS-422 cable contains a twisted pair. We can form a point to point network linking up to 10 devices (1 driver and 10 receivers) and up to 1200 meters in length. It operates in differential mode on levels +6V -6V and can reach speeds up to 10Mb/s. It can operate in half-duplex or full duplex with 4 cables.