Documentation issue statusVersionChanges4.0.0Update chapter "Use of SFP in the CU1521-0020"Update chapter "Technical data"Update chapter "Application notes"Update chapter "Firmware compatibility"3.9.0Chapter "Use of SFP in the CU1521-0020" addedChapter "Object description and parameterization CU1521-0020" addedUpdate chapter "Application notes"Update chapter "Firmware compatibility"Update chapter "Diagnosis"3.8.0Update chapter "Technical data"Update chapter "Application notes"Update chapter "Firmware compatibility"Structural update3.7.0Update chapter "Technical data"Update chapter "Basics of fiber optic technology"Structural update3.6.0Chapter "Technical data" updatedStructural update3.5.0Chapter "Technical data" updatedChapter "Application notes" updatedStructural update3.4.0Structural update3.3.0Chapter “Introduction” updatedChapter "Firmware compatibility" updatedChapter "Operating and usage instructions"Structural update3.2.0Chapter "Technical data" updatedChapter "Basics of fiber optic technology" updatedStructural update3.1.0Chapter "Technical data" updatedChapter “Power Supply Wiring” addedStructural update3.0Chapter "Technical data" and "Dimensions" updatedChapter "Disposal" addedStructural update0.1 – 2.9*archived*