a modular system for the control of at least one compression system for the compression a fluid medium , said compression system comprising compressors and their controllers for the compression of the fluid medium , secondary treatment devices for the treatment of the medium delivered from the compressors , and piping systems for conducting the fluid medium to a place of consumption , said control system comprising a control unit containing a data processing system for controlling the compression system , a user interface including a display assodated with it and transmission means for the transmission of control data between the control unit , the controllers and pressure sensors . the transmission means consist of data communication buses , preferably serial communication buses and a data communication port unit serving to connect the bus to the control unit . the controllers and pressure sensors are connected to common data communication buses .