The invention relates to an adapter equipment (IWF), a method and an arrangement for setting up a data call terminating at a subscriber in a telecommunication network. In the invention, adaptation functions of two or more data services are integrated into a single adapter pool that has one common MSISDN number shared by all the data services. After the connection has been set up, the IWF does not try to synchronize itself according to any data service towards another network but it monitors a traffic channel arriving from the other network (ISDN, PSTN) in order to identify the data service used by the calling terminal equipment. After the IWF has identified the data service, it starts operating in the manner required by the identified data service and data transmission may begin.