The combination of two geometric forms reinterprets the design of subscriber terminal equipment in a pleasant way and, at the same time, conveys the ease of handling the unit. The casing of the FTTH modem for fibre-optic connections has been conceived in such a way that modules can be installed individually or in combination with other modules. The user simply attaches these to the unit through an easy click-on system, thereby considerably reducing technical efforts and additional expenses.