DIN EN IEC 61158-4-21 : 2020 Title: Industrial communication networks - Fieldbus specifications - Part 4-21: Data-link layer protocol specification - Type 21 elements (IEC 61158-4-21:2019); English version EN IEC 61158-4-21:2019, only on CD-ROM Year: 2020 Publisher: DIN Media GmbH Availability: Within 1-2 working days