As automation becomes more thoroughly networked with advances in speed, connectivity, and security; this fifth edition of an ISA best seller is still designed to give technical professionals with little or no background in data communications the knowledge they need to succeed. Additionally, even those with nominal knowledge will find information to enhance troubleshooting and to understand both legacy systems and the more advanced systems now being installed throughout automated facilities. As before, the text emphasizes the practical aspects of commonly used systems rather than design criteria. It contains a complete description of the relevant terminology, standards, and protocols including EIA/TIA-232/485, IEEE 802.3, IEEE 802.11, and IEEE 802.15. New material in this edition includes information on updated Ethernet and router technologies; a more detailed description of VPNs; and expanded information on cybersecurity (including ANSI/ISA/IEC 62443). A complete glossary and index allows the book to be used as a handy reference. SCADA, DCS, and fieldbus systems are all explained, as well as operating system considerations from a communications perspective. This is a book for newcomers to automation data communications, as well as a reference for those who are currently working in the field.