A combination of a functional unit a receiving unit and a fastening device for releasably fastening said functional unit in a connection direction to said receiving unit, said functional unit and said receiving unit each having a longitudinal direction, a transverse direction and a height direction, said functional unit further having a functional unit abutment surface, and said receiving unit further having a receiving unit abutment surface, said functional unit abutment surface and said receiving unit abutment surface being adapted for abutting against each other in the connected state, said fastening device further comprising at least one pair of magnets, at least one functional unit magnet being allocated at or close to the functional unit abutment surface, and at least one receiving unit magnet being allocated at or close to the receiving unit abutment surface, said magnets (112, 114) of said at least one pair of magnets exerting an attractive force to each other, said fastening device further comprising at least one mechanical locking unit comprising a functional unit locking element allocated to the functional unit and a receiving unit locking element allocated to the receiving unit, said locking elements (130a, 130b) being adapted and intended to cooperate with each other, characterized in that said functional unit includes a communication device, the at least one mechanical locking unit is designed as a snap-lock unit, comprising at least one catch element and at least one trap element, adapted and intended to cooperate with each other, and the fastening device further comprises a securing element, said securing element being transferable between a securing position and a releasing position, said securing element being adapted to prevent in its securing position a movement of the functional unit relative to the receiving unit in a detaching direction, while allowing such movement in its releasing position, a deflection direction of a catch end of the at least one catch element extending substantially parallel to a first direction, namely the transverse direction or the longitudinal direction, the detaching direction extending substantially parallel to a second direction, namely the longitudinal direction or the transverse direction, i.e. substantially orthogonal to both, the deflection direction and the connection direction. said functional unit and said receiving unit each having a longitudinal direction, a transverse direction and a height direction, said functional unit further having a functional unit abutment surface, and said receiving unit further having a receiving unit abutment surface, said functional unit abutment surface and said receiving unit abutment surface being adapted for abutting against each other in the connected state, said fastening device further comprising at least one pair of magnets, at least one functional unit magnet being allocated at or close to the functional unit abutment surface, and at least one receiving unit magnet being allocated at or close to the receiving unit abutment surface, said magnets (112, 114) of said at least one pair of magnets exerting an attractive force to each other, said fastening device further comprising at least one mechanical locking unit comprising a functional unit locking element allocated to the functional unit and a receiving unit locking element allocated to the receiving unit, said locking elements (130a, 130b) being adapted and intended to cooperate with each other, characterized in that said functional unit includes a communication device, the at least one mechanical locking unit is designed as a snap-lock unit, comprising at least one catch element and at least one trap element, adapted and intended to cooperate with each other, and the fastening device further comprises a securing element, said securing element being transferable between a securing position and a releasing position, said securing element being adapted to prevent in its securing position a movement of the functional unit relative to the receiving unit in a detaching direction, while allowing such movement in its releasing position, a deflection direction of a catch end of the at least one catch element extending substantially parallel to a first direction, namely the transverse direction or the longitudinal direction, the detaching direction extending substantially parallel to a second direction, namely the longitudinal direction or the transverse direction, i.e. substantially orthogonal to both, the deflection direction and the connection direction.