Transas Marine has extended its range of GMDSS simulators by introducing the TGS 4000 system. The new TGS 4000 simulator complements and enhances the existing TGS 2000 and TGS 3000 versions, by offering a number of new features which reflect the latest developments in shipboard communication equipment, based on modern PC environment. The GMDSS simulator TGS 4000 includes one Instructor workplace and up to 16 Student workstations operating under Windows NT. In addition to the functionality gained in the previous versions, the TGS 4000 simulates communications via Inmarsat-B ship earth stations. The TGS 4000 offers the added facility for airplane communications using AERO VHF on the aircraft emergency frequencies. The new simulator provides realistic simulation of radio wave propagation.