This paper studies an M/M/c type of queueing model with (Ri,ri) switch-over policy. When there are i machines in operation, one machine will be deactivated if the queue length drops to a predetermined level ri, and an additional machine will be activated if the queue length increases to another predetermined level Ri(>ri). This type of queueing model has applications in production/inventory systems when more than one machine is available and the continuous review inventory policy is applied. The steady-state probabilities of the queue length and some other measures of performance, such as the mean queue length and the number of machines activated during a production cycle, are derived. The optimal values of the parameters (Ri,ri) are studied and a number of different numerical examples are given.
