Hello, Have you seen this document?http://www.doepfer.de/pdf/A154_155_Connection.pdfmaybe with this photo you can see better how the different parts are connected- Blue connections to the bus- Pink connections for sending a message between modules- Yellow power connection from one module to another (attention to the A-155 S1 must remain free)http://i56.serving.com/u/f56/17/81/92/13/a154a110.jpg