A computer is connected to three terminals (for example, measuring devices). It can simultaneously evaluate data records from only two terminals. When the computer is processing two data records and in the meantime another data record has been produced, then this new data record has to wait in a buffer when the buffer is empty. Otherwise the new data record is lost. (The buffer can store only one data record.) The data records are processed according to the FCFS-queueing discipline. The terminals produce data records independently according to a homogeneous Poisson process with intensity The processing times of data records from all terminals are λ. independent (even if the computer is busy with two data records at the same time) and have an exponential distribution with parameter µ. They are assumed to be independent of the input. Let be the number of data records in computer and buf- X(t) fer at time t.