A connection system for connecting a built-in appliance to a furniture unit is provided and includes a securing strip having first securing elements for securing to the furniture unit side of the securing strip and second securing elements for securing to the appliance side of the securing strip and at least one cover strip which can be attached to the securing strip. The valve assembly includes a valve stem having a head portion which engages with a valve seat in order to close and seal the valve and an elastically deformable portion. The AG generates a third key for mutual authentication between the AG and the AT. To further improve the optical performance of the system, these TIR prisms can be attached directly to the SLM package 300, completely eliminating the package window. A locking means is provided which prevents a reverse rotation of the belt reel in the unwinding direction, after the pretensioning drive has driven the belt reel in the wind up direction and has thereby pretensioned the safety belt.