Switching the physical channel while maintaning the communication link is a feature of both cordless and mobile systems. In this paper we consider the Dynamic Channel Selection (DSC) algorithm of the Digital European Cordless Telecommunications ( DECT) system. This algorithm is used in the radio interface between the portable parts and the fixed part The main feature this algorithm is that the Portable Parts select the radio channels and time slots for the call. In GSM, another mobile radio system, the basestations control the allocation of these resources although assisted by the mobiles. We specify the DECT algorithm as a refinement of the GSM system.