Abstract: An essentially parallelepiped-shaped housing has a slide at which there is formed a drawer-like constructed compartment for the reception of a current source. In the closed position of the slide such coincides with one of the base surfaces of the housing. During the course of an opening movement the slide initially frees the compartment, and thereafter, during a further opening movement, frees access openings for adjustment or tuning elements or the like located at the side of the housing body dispositioned opposite the compartment. Operatively associated with the first opening step for freeing the compartment are stops over which there can travel the slide. Equally, stops are operatively associated with the slide for the further opening step for freeing the access openings.