A communication bus (B1, B2, Bp) in a motor vehicle (110) transfers electrical signals between the nodes (N1, N2, N3, Nn, N21, N2m, Np1, Npr) included in the motor vehicle. The communication bus comprises two unshielded signal lines (S1, S2) and a decoupling line (D), which are configured so as to divert undesired electromagnetic radiation deriving both from external systems that are not connected to the communication bus (B1, B2, Bp) and the electrical signals transferred via the unshielded signal lines (S1, S2). The decoupling line (D) is connected for alternating current to a ground potential in one and only one (N3) of the nodes (N1, N2, N3, Nn, N21, N2m, Np1, Npr) included in the communication system.