eng Ansari Education and Research Society Journal of Ultra Scientist of Physical Sciences December 2008 20 3 659 662 jusps-B 1389 article J. GEETHA 1 SULAIMAN 2 R. SATHIYAMOORTHI 3 Department of Mathematics, Nehru Memorial College, Trichy (INDIA) Department of Mathematics, Jamal Mohammed College, Trichy (INDIA) Department of Statistics, (Retd. ) Annamalai University, Chindamabarm (INDIA) <p style="text-align:justify">When two machines M₁ and M₂ are in series the output of M₁ which is the semi finished product is the input for M₂. If M₁ goes to the down state the supply or input to M₂ is stopped and M₂ goes to the down state. The idle time cost of M₂ is high and prohibitive. Hence a reserve of semi finished product in between M₁ and M₂ is suggested. In this paper the optimal reserve size is determined under the assumption the interarrival times between breakdowns of M₁ is a random variable which undergoes a parametric change after a truncation point which is also a random variable. Numerical illustration is also provided.<br /> &nbsp;</p> https://ultraphysicalsciences.org/paper/1389/ System in Series Optimal Reserve Change of parameter.