Thank you for the information. The dongle seems to be made just from two specific connectors with a given wiring scheme (no special electronics necessary). As it seems, the same modem card was made in different flavours just by using different connectors on the pcb, probably with some specific connections regarding to different telephone device specifications. Someone even managed to convert a mini-8 type into a RJ11 type, as mentioned here. If someone has not lost the 8-pin modem dongle, could he or she probably take the time to measure the electric connections and set up a description? A mini 8-pin to RJ11 wiring scheme would be nice, but any localised version should do, as information about national telecommunications standards should be available.