When it is time for setting old systems ashore and letting new systems in, the SeaCom telephone and intercom system is a perfect choice. The vessels having the age to be refit, wil more or less always have 2 wire only telephone systems.
The only choice is a new and moden telephone and intercom with 2 wire only telephones. Changing a telephone system and its telephone is a huge job, but rewiring the full ship replacing the 2 wires by ethernet cables is always beyond what is possible.
The SeaCom 3000 and SeaCom 2100 are the right choice. Although these telephone systems are fully computerised and internally digital, the extensions line are 2 wire only, allowing for reusing cables on board.