Let M be a closed manifold and˛W 1 .M / ! U n a representation. We give a purely K-theoretic description of the associated element in the K-theory group of M with R=Z-coefficients (OE˛ 2 K 1 .M IR=Z/). To that end, it is convenient to describe the R=Z-K-theory as a relative K-theory of the unital inclusion of C into a finite von Neumann algebra B. We use the following fact: there is, associated with˛, a finite von Neumann algebra B together with a flat bundle E ! M with fibers B, such that E˛˝E is canonically isomorphic with C n˝E , where E˛denotes the flat bundle with fiber C n associated with . We also discuss the spectral flow and rho type description of the pairing of the class OE˛ with the K-homology class of an elliptic selfadjoint (pseudo)-differential operator D of order 1.