Abstract: In order to test the operatability of the section which dispenses a hose-shaped foil from a foil storage, which hose-shaped foil is advancable by one seat length after each use of the lavatory by means of a drive and a spent foil take-up means a check is made prior to every advancing operation if foil is still present in the foil storage. A detecting system checks if the hose-shaped foil moves, whereby simultaneously the current for the operation is checked. If such is the case a control signal is generated which indicates the operatability of the said end can be used, for instance, for deblocking access to the lavatory.