The BfS operates a gamma dose rate measurement network with about 1800 probes, uniformly distributed over Germany. The automatically working systems compare the actual level of radiation with the long term mean and sends an alert to the data centers immediately, if the radiation exceeds the threshold value. This network is a part of the German early warning system, in case of a nuclear accident. Hardware of data logger and probes as well as software are developed in-house by the BfS. On the mountain Schauinsland the BfS operates an international measurement station for gamma dose rate probe calibration and long term tests.