A communication system linking different rooms within a building or ship etc WordNet 3.0 & Open English WordNet

An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the public telephone network. Wikipedia

A stand-alone voice communications system for use within a building or small collection of buildings Wikipedia Disambiguation

Communications system; a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network Wikidata

An electronic communication system, especially one between rooms in a building. Wiktionary

An electronic communication system. Wiktionary (translation)