The invention provides a dual-specific ligand comprising a first immunoglobulin variable domain having a first binding specificity and a complementary or non-complementary immunoglobulin variable domain having a second binding specificity. The inner heat exchanger housing and the outer heat exchanger housing are connected to one another in a second axial end area and a fluid flow space is formed between the inner heat exchanger housing and the outer heat exchanger housing. A procedure of automatic dial-up connection to Internet is composed, where the automatic dial-up connection procedure includes a user data.