Traditional videoconferencing systems, while allowing users to view remote collaborators, do not support ``gaze awareness,'' that is, do not allow a user to make eye contact with a specific collaborator. When a user looks at the camera, it is not clear which collaborator he is directing his communication to. Hydra [] provides special devices to address this problem, each of which has a camera and a display. Each remote collaborator is assigned a Hydra device which displays his image, and the camera in that device captures the local image transmitted to him. Thus, when the user turns to a device, all collaborators know who he is looking at. A single microphone captures the local audio transmitted to all users and all remote audio streams are combined into one stream played through a single speaker.
Hydra, thus, better creates the illusion of ''being there,'' but still comes up a bit short in some dimensions. The hydra devices are small, therefore users see miniature images of their collaborators. Moreover, since the devices are independent with distinct boundaries, the system does not create the illusion of the collaborators being located in one room. Finally, the single microphone and speaker does not allow audio directionality.