Fieldbus Foundation has announced that it has enhanced its open, non-proprietary Foundation fieldbus physical layer technology. The updates to the H1 (31.25kbit/s) physical layer specifications will improve the robustness of fieldbus control systems by optimising device interoperability and integration. According to Fieldbus Foundation, end users will benefit from easier installation, faster commissioning and seamless start-ups. Enhancements include: addition of a test procedure for isolated couplers to the existing Foundation fieldbus coupler test specification – registration of isolated couplers is now possible; and improvements to the H1 physical layer conformance test specification based on action requests received during the last few years – significant changes include the addition of a receive jitter test case and a device coupler interoperability test. Further improvements include: updates to the H1 physical layer test specification to remove obsolete profiles and align references in the document with the current International Electrotechnical Commission (IEC) specifications – coupler profiles were also added to the test specification; and miscellaneous updates to the Foundation fieldbus cable specification.