The increase of communication eficiency brings an enormous gain in performance of all business activities in an ofice environment. In particular, teleconferencing is attracting a great deal of attention due to advantages it creates, such as reduction of cost and time spent in conferences and meetings. LANBRETA-GCS is a LAN based real time audio-graphics teleconferencing system that is being developed by PUC/RJ and RIO-SC of IBM Brad and is the subject of this paper. The paper's first part classifies the system within a taxonomy based on observations of various other systems' characteristics. The second part deals with the specification of the system. At first, the environment where the system is being implemented is introduced. Then, the general specification is presented, together with justifications of the several choices made. Although LANBRETA-GCS is being implemented in a local area network environment, utilizing an IBM token ring and the functions of DOS, NETBIOS and the PC LAN Program, its implementation is much more general. The current implementation is just an example among many other possible implementations. This implementation is commented within the text, in order to demonstrate the system's viability in a local area network environment.