The GTS consists of an integrated network interconnecting meteorological telecommunication centres of National Meteorological and Hydrological Services (NMHS) worldwide. It comprises point-to-point circuits, point-to-multi-point circuits for data distribution, multi-point-to-point circuits for data collection, as well as two-way multi-point circuits. These circuits are a combination of terrestrial and satellite telecommunication links. Radiosondes are launched from worldwide stations on the GTS network.