Abstract: An expandable and modular intercom and annunciation system includes a plurality of signal sources, such as smoke detectors, breakage detectors, intrusion detectors, telecommunication detectors (such as ringers), and gas detectors. The system further includes a plurality of originating interface modules, each respectively coupled to a signal source for receiving signals from the corresponding plurality of signal sources and for converting the signals to common communication protocol signals. The system also includes a receiving interface module coupled to the plurality of originating interface modules for communication via the common communication protocol, and an intercom and annunciation unit coupled to the receiving interface module to receive the common communication protocol signals. The intercom unit has a processor, a memory, and a user interface including an audio output.