An infinite buffer with general arrival process, synchronous transmission, one single output channel and random server interruptions is considered. As opposed to previous analyses the interruption process of the output line is kept rather general, i.e. the server is assumed to be in one of two states, “available” or “blocked”, where the sojourn time of the blocked state is arbitrarily distributed and the sojourn time of the available state has a density function which is a mixture of a finite number of geometric densities. For this general case the probability generating function of the buffer occupancy at various time instants is derived. The results of the study are applied to the case where the server interruptions are due to the presence of speech at the input of the transmission channel of an integrated voice-data system. Some considerable deviations from earlier results are found.