the terminal device ms the terminal device ms then utilizes this checking software sw in order to perform its own checking the address adr of the checking center sc used for transmitting the request signal s 1 is advantageously valid for all possible communication systems in which the terminal device ms can be operated for example after it has been made fit for use by appropriate software downloads for such types of systems in each case the address adr can for example be a particular telephone number valid for all communication networks such an address adr would then be comparable with the emergency telephone numbers commonplace today which are standardized in a great diversity of mobile radio systems in germany for example this emergency number is u201c 112 u201d the invention is suitable for use in any desired terminal devices ms which can be reconfigured by software downloads it is suitable for use in any desired radio communication networks in which such types of reconfigurable terminal devices can be used it is also possible that instead of only one checking device sp a plurality of checking devices sp sp u2032 and also possibly the terminal device itself ms simultaneously perform checking of the functional integrity of the terminal device ms while it is operating this is likewise defined by the checking center sc in this situation any of the units involved in such a.