A microphone-speaker device includes a speaker, a microphone configured to capture sound and output an audio data signal and a housing configured to contain the microphone and the speaker. The device also includes an electronic circuit having audio electronics coupled to the speaker, an Ethernet interface configured to connect the electronic circuit for communication with a security system through an Ethernet connection, a power extractor for extracting power from the Ethernet connection for powering the electronic circuit and the microphone, and processing electronics configured to process the audio data signal from the microphone.