thickness t1 of approximately 8 6 millimeters as already stated the apparatuses of the proposed digital system are designed to be 34 backwards compatible with 34 that is largely the same at least mechanically as those of able to play cassettes from the known compact cassette system as well as the new digital cassettes for this reason the cassettes belonging to the digital system should provide the same room for cooperation with a pressure roller as the cassettes belonging to the compact cassette system for this purpose fig3 shows sectional views of different cassettes at the location of the pressure roller openings the dimension a of the pressure roller opening in the known compact cassette 51 in a direction perpendicular to the mains walls 53 and 55 is 9 6 millimeters and consequently larger than the thickness t1 of the described digital cassette 1 main wails 5 and 53 of both cassettes 1 and 51 respectively cooperate with a surface a of the apparatus the pressure roller apertures in the housing of cassette 1 extend into two main wails 4 5 and the pressure roller opening in its sliding cover extend into the two main portions 25 27 respectively as a result of this the main wails 4 5 and the main portions 25 27 of the cassette 1 do not obstruct a pressure roller of a maximal dimension a in a direction perpendicular to the main wails in the present example the cassette 101 in accordance with the invention has a thickness t2 of 9 6 millimeters the main portion 127 of the sliding cover of this cassette has.