Intercom vs. Entryphone

Intercomnoun

an electronic communication system, especially one between rooms in a building

Intercomverb

(ambitransitive) To communicate (with) by intercom.

Intercomnoun

a communication system linking different rooms within a building or ship etc

Intercom

An intercom () or interphone is a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network. Intercoms are generally mounted permanently in buildings and vehicles.

Entryphonenoun

An intercom system which enables someone, without opening the door, to converse with the person who has rung the doorbell.