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The letters A and B are inversed comparing the RS 485 driver with the PROFIBUS connector. Any explanation?

April 26, 2017comparing connector driver explanation inversed letters PROFIBUS Rs

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The letters A and B are inversed comparing the RS 485 driver with the PROFIBUS connector. Any explanation?

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In the late 1980’s when PROFIBUS FDL and the DB9 connector were standardized the PROFIBUS wires were accidently named B and A, without looking at the designation on the existing RS485 drivers. After PROFIBUS was standardized there was no possibility to change it anymore. We know that it is very confusing for beginning product developers, but luckily the end-user does not have to get involved with RS485 drivers.