A group audio teleconferencing system (GATS) is an audio communications link between groups of people in different locations. Its operation depends in a complex manner on the operation of the system components: room acoustic environments, terminal equipment, transmission facilities, and conference bridges. The main problems encountered are room reverberation, room and circuit noise, chopping of speech by voice switching, and loss contrast (differences in speech levels from various rooms). Solutions to problems of reverberation will be discussed in accompaning papers (Stockbridgeet al.and Curtiset al.). This paper discusses solutions to the problem of loss contrast, in particular, use of standard level sound source in alignment and testing of GATS. References will be made to a working example of GATS—the General Service Administration Teleconference System.