The UCAM cameras have built in microphones allowing you to hear the audio and record this in addition to the video.
The indoor version of the camera has an additional function and allows for the camera to transmit audio through a set of speakers.
The camera is designed with a 3.5mm "headphone" style jack at the rear and this allows you to attach a set of speakers to this. These speakers will want to be independently powered in order to achieve a usable volume as non powered ones running off the 12 volts the camera uses will be very quiet, even at the loudest volume setting.
To activate the two way audio open your app and tap your indoor camera to start streaming the live feed. On the page tap the microphone symbol to activate the microphone on the phone. You can then talk into the phone and transmit audio to the camera via the speakers.
This feature is not present in the outdoor versions of the camera, these only have a microphone to pickup audio at the camera location.