Abstract
We characterize interval Mobius number systems with sofic expansion subshifts and show that they can be obtained as factors of interval Mobius number systems with expansion subshifts of finite types. The endpoints of interval cylinders of such systems can be computed by a simple formula which generalizes the computation of Farey fractions in the Stern-Brocot graph.
We treat in detail the bimodular number system which has many nice properties and could be used for exact real computer arithmetic.