Electrical – How is this junction box intended to be used


I am in Europe and recently purchase this junction box:

junction box

I have two questions:

  1. What is the intended use of the two brass colored busbars versus the three steel colored busbars?
  2. What is the intended use of the straight busbar in the middle versus those curved busbars on the periphery?

Best Answer

  1. neutral and ground vs three phases.
  2. ground

Note the "N" and ground-symbol moulded on the plastic base.