V.P. Koryachko - Dr. Sc. (Eng), Professor, Head of Department "Systems of automated design of computing facilities", Ryazan State Radio Engineering University. E-mail: sapr@rsreu.ru
O.V. Lukyanov - Post-graduate Student, Department of "Systems of automated design of computing facilities", Ryazan State Radio Engineering University, Head of the Department of FGUP "Space Rocket Centre "TsSKB - Progress" - "OKB Spektr". E-mail: luk_ov@mail.ru
A.P. Shibanov - Dr. Sc. (Eng), Professor, Department of "Systems of automated design of computing facilities", Ryazan State Radio Engineering University. E-mail: mail@shibanov.ryazan.ru

The method of determination of intervals employment and downtime ground measuring complex, producing reception and transmission through the communication channel information from measuring systems. Mode of operation of the complex stationary. The input buffer of the communication channel come Poisson packet streams that are transmitted into the communication line in the order of their coming. The loss of packets in the buffer are excluded. Set distribution execution time of operations of the Protocol packet and the probability of their choice. Reducing of the period of employment of the complex is achieved by decreasing the mean time of a packet transmission over the communication channel and its variation with the use of GERT-networks. This is possible if the time of passing of at least one path from source s to flow t random with a multimode probability distribution or with single-mode distribution with long-th "tail". Reduce the tails of the distributions can decrease the transition probabilities for cycles or reduction of the time of passing of these cycles. Determined by the partial graph H GERT-network to: - P a loop of the first order, not including the source s and runoff t, and has at least one common site of i-th a simple s-t-path; - Q is a loop of the first order, not including the source s and runoff t, and has at least one public site with j-th simple s-t-path; - any loop P and Q, belonging to different s-t-paths are not public sites. Then a set of branches and units of the i-th simple s-t-path and the set of all loops P a partial graph H i-th a simple s-t-path. Partial graphs H reflect the functioning of the parallel component of the protocol packet. An example of transformation GERT-network protocol decomposed into partial graphs H. The output variable of the original GERT-network has a multimode distribution and unacceptable values of the mathematical expectation and dispersion. Is step-by-step improvement of the performance of GERT-network: - are the distribution density of the output values graphs H; - reduced transition probabilities cycles to obtain single-mode distributions graphs H; - minimisation of the squares of the differences of the mathematical expectations of cases tea values that determine the fashion graphs H; - reduced mathematical expectations and intervals 3σ output values graphs H; - calculated the period of employment using the queuing system M/G/1.