In conventional systems, a soft terminal (e.g. a Personal Computer, PC, client, etc.) and a mobile terminal can be implemented to use the same number and vibrate simultaneously with each other. This interconnects the PC client and the mobile terminal which serve as the major two entities of an enterprise. However, the interoperability there between is not satisfying enough. For example, when a user is calling with a called party via the PC client, if he has to leave his office for an unpredictable reason and meanwhile wants to maintain the current call, the call on the PC client cannot be switched to the mobile terminal of the same number. On the other hand, if he comes back to his office, the call on the mobile terminal cannot be switched to the PC client either of the same number.