RS-422 and RS-485 Standards Overview and System Configurations

ANSI TIA/EIA-422 and TIA/EIA-485 standards, commonly known as RS-422 and RS-485, respectively, specify balanced data-transmission schemes for transmitting data over long distances in noisy
environments. These standards are compared, and their basic differences and similarities are discussed. Techniques for impedance matching to minimize line reflections in several applications are presented, with
laboratory test results.