A ceiling plate provided at a ceiling portion of a process chamber that may be evacuated to a vacuum is disclosed. General programming media elements are selected for output in a public space based upon a source indicating available media elements, and upon transient variables especially pertinent to the public space, which are provided independently of user inputs. A first region of the disk includes data recorded for a first logical disk, and a second region is adapted to store data for a second logical disk, and the first and second regions are located on the two layers. The housing is attachable to the platform at a pivot point and has at least one axle adapted to receive at least one wheel.