What is the mandatory safety equipment required for a tractor power take-off drive shaft (Zapfwelle / Gelenkwelle)?

1. A guard covering only the two universal joints, leaving the shaft tube exposed
2. A warning decal on the shaft together with a chain restraint
3. A metal mesh cage fitted around the implement input shaft only
4. A complete, undamaged protective tube and funnel guards (Schutzrohr und Schutztrichter) enclosing the whole shaft and both universal joints