Two Queues Attended by a Single Server

It is supposed that customers of type 1 and type 2 arrive at a service system in accordance with a Poisson process. There are two counters in the system. Customers of type 1 receive service at counter 1 and customers of type 2, at counter 2. The customers are served by a single server who attends the two counters alternately. At each counter the service times have a general distribution. This paper is concerned with the determination of the distribution of the waiting time of a customer in a stationary process.