Download the user guide for Central Station 3 in English from the Märklin web-site:
https://static.maerklin.de/damcontent/cf/18/cf189b8af3996329dc65f76cde1e52651482230603.pdf
Download the user guide for Central Station 3 in English from the Märklin web-site:
https://static.maerklin.de/damcontent/cf/18/cf189b8af3996329dc65f76cde1e52651482230603.pdf
Märklin 6021 Control Unit - connection table
Plug- and cable colors in the Märklin system (PDF-File)