An online social network is managed using one server for database management tasks and another server, preferably in a distributed configuration, for CPU-intensive computational tasks, such as finding a shortest path between two members or a degree of separation between two members. In accordance with the present invention the protective circuit comprises a semiconductor switch which is inserted between the coil and the second potential and, in the event of a voltage reduction or potential reversal, isolates the coil from the second potential, so that the discharge from the coil has no adverse effect on the energy supply system or the intrinsic safety. The default user interface files can comprise one or more of a structure definition file, a content definition file, and a content display file.