one another such that they form a housing frame that is designated 82 as a whole has a preferably rectangular external contour 84 rises between the mounting side 64 and the access side 68 and is accessible in particular from the access side 68 preferably the mounting side 64 and the access side 68 extend in mutually parallel planes with the result that the housing frame 82 rises above the mounting side 64 to the access side 68 by an extent that is the same on all sides a controller housing unit that is designated 88 as a whole is placeable on the connector housing unit 48 the controller housing unit 88 includes an electronic functional unit 92 for performing one or more different compressor functions such as protective monitoring controlling diagnostic communication and regulating functions which will be described in more detail below by way of example the controller housing unit 88 itself has a mounting side 94 and extends as far as an access side 98 wherein a carrier base 96 is arranged between the mounting side 94 and the access side 98 preferably lies close to the mounting side 94 and carries the electronic functional unit 92 the controller housing unit 88 also includes housing outer walls 102 104 106 and 108 wherein preferably the housing outer walls 102 and 104 and the housing outer walls 106 and 108 extend parallel to one another and thus form a rectangular housing frame 112 preferably the housing frame 112 of the controller.