It is a PC-based simulator to train sea-faring people in the use of GMDSS communications equipment, within a controlled and safe environment. Vox Maris simulates VHF (DSC), MF/HF (DSC) and Navtex fully operational features, as far as their GMDSS operational procedures. Others external issues, as real conditions of maritime communications are simulated too. Vox Maris offers features for two different roles The instructor of the course and the students. The instructor designs exercises in order to evaluate knowledges and actions of the students. The exercises can have a specified goal that students would have to reach. Vox Maris help the instructor to know when a practice is going out of the goal, thus, he can correct the direction of the simulation. In a simulation excercise, students establish communications using several GMDSS equipments. They have to do the same procedures on the simulator as in the real equipment.