An apparatus comprising an electronic data processing system which has at least one means for electronic data processing, wherein the apparatus is configured to perform a method of checking an operation of the at least one means, wherein the method comprises: - operating the means using a first data type to obtain a first operating result, wherein the operation of the means using the first data type comprises processing a first value (v) of the first data type using a first calculation function (f) to obtain a first calculation result (v') which represents the first operating result in the first data type; - operating the means using a second data type to obtain a second operating result, wherein the operation of the means using the second data type comprises generating a second value (w) and processing the second value (w) of the second data type using a second calculation function (g) equivalent to the first calculation function (f) to obtain a second calculation result (w') which represents the second operating result in the second data type; - comparing the first operating result and the second operating result using at least one predefined test criterion; and - generating a signal when the at least one predefined test criterion is infringed, characterized in that the second value (w) of the second data type is generated by transforming the first value (v) of the first data type into the second value (w) of the second data type using a first transformation function (t); the first calculation result (v') is transformed using the first transformation function (t), with the transformed first calculation result (w") representing the first operating result in the second data type; the first operating result and the second operating result are compared by checking the transformed first calculation result (w") and the second calculation result (w') for equivalence; and the apparatus has at least one sensor for monitoring a monitored zone, with data of the sensor being processed using the means in order to determine whether the monitored zone is infringed. - operating the means using a first data type to obtain a first operating result, wherein the operation of the means using the first data type comprises processing a first value (v) of the first data type using a first calculation function (f) to obtain a first calculation result (v') which represents the first operating result in the first data type; - operating the means using a second data type to obtain a second operating result, wherein the operation of the means using the second data type comprises generating a second value (w) and processing the second value (w) of the second data type using a second calculation function (g) equivalent to the first calculation function (f) to obtain a second calculation result (w') which represents the second operating result in the second data type; - comparing the first operating result and the second operating result using at least one predefined test criterion; and - generating a signal when the at least one predefined test criterion is infringed, characterized in that the second value (w) of the second data type is generated by transforming the first value (v) of the first data type into the second value (w) of the second data type using a first transformation function (t); the first calculation result (v') is transformed using the first transformation function (t), with the transformed first calculation result (w") representing the first operating result in the second data type; the first operating result and the second operating result are compared by checking the transformed first calculation result (w") and the second calculation result (w') for equivalence; and the apparatus has at least one sensor for monitoring a monitored zone, with data of the sensor being processed using the means in order to determine whether the monitored zone is infringed. <EOS>