Marine DNV-GL type approved VoIP telephones are rare species. But don't worry. VoIP exchanges do have FXS ports to which our SC220, SC411 and SC421 will connect.  In that way You can implement fully DNV-GL type approved communication to technical spaces like engine room, steering geer room truster room etc. fully integrated in the overall VoIP telephone system.
Make sure to distribute 24V DC to the SC411 and SC421 stations.