A communication system in which an availability of communication resources to be used by a first base station module and a second base station module of a communications apparatus is managed. The subject bifunctional molecules are conjugates of a drug moiety and a pharmacokinetic modulating moiety, where these two moieties are optionally joined by a linking group. A device installed into the return pipe counteracts volume flow pulsations by damming up the hydraulic fluid return flow. The first and second compartments are separated from each other.