BS EN 61158-4. ndustrial communication networks. Fieldbus specifications. Part 4-1. Data-link layer protocol specification. Type 1 elements. Part 4-2. Data-link layer protocol specification. Type 2 elements. Part 4-3. Data-link layer protocol specification. Type 3 elements. Part 4-4. Data-link layer protocol specification. Type 4 elements. Part 4-11. Data-link layer protocol specification. Type 11 elements. Part 4-12. Data-link layer protocol specification. Type 12 elements. Part 4-13. Data-lin"