Experiments on mobile satellite communications are being carried out to prove if they are technically feasible for future domestic satellite services in the Experimental Mobile Satellite System (EMSS) project using Engineering Test Satellite-V (ETS-V). Furthermore, experimental ISDN basic-rate communications services have also been performed for marine vehicles. This paper describes the Configuration of an experimental system for maritime ISDN satellite communications, and the characteristics of ISDN basic-rate interface connections for the digital telephones, G4 facsimiles, and color video-phone terminals of terrestrial ISDN services. This experiment provided a lot of information for designing future mobile satellite communications systems. Moreover, it clarifies that FEC (Forward Error Correction) in a mobile satellite link with poor transmission quality is very effective at improving the communication quality of mobile satellite systems.