A group of network devices, such as Ethernet switches, are logically configured as a single cluster, with one commander device and one or more expansion devices. The locking element is moved towards the unlocking position through a one-way transmission of the actuating element upon a movement of the flap into its closed position or beyond thereof, respectively, and the locking element completely engages the catching element upon arrival of the flap at its closed position. The printhead includes a seal membrane joining the moving portions to the printhead.