The bidirectional multi-drop network shown on this slide is not very practical. Because RS-422 allows only one driver on a bus, each slave that talks back to the master needs a separate twisted pair, and the separate busses mandate an additional receiver in the master for each slave it must listen to. Obviously this gets very expensive, so RS-422 typically is used for only point-to-point or multi-drop applications such as control systems, rather than for bidirectional data collection systems.