There are three common connection schemes used in interface networks. On the left is point-to-point, which can be used with either RS-422 or RS-485. Point-to-point means there is just one transmitter talking with only one receiver on a bus. A point-to-point RS-422 network is often used as an RS-232 “extension cord” to extend the transmission distance of RS-232 control lines. The multi-drop – or broadcast – network is the middle example. It has only one transmitter on the bus, but allows multiple receivers. Both RS-422 and RS-485 can operate in this configuration. RS-485 is the most flexible standard, allowing for multi-point operation, where it is possible to have multiple transmitters and receivers all on the same bus. For all schemes, a ground connection between nodes is recommended to control common mode voltage differences, and to minimize EMI.