  Efficient use of call center operators through technological innovations more
often come at the expense of added operation management issues. In this paper,
the stationary characteristics of an $M/G/1$ retrial queue is investigated
where the single server, subject to active failures, primarily attends incoming
calls and directs outgoing calls only when idle. The incoming calls arriving at
the server follow a Poisson arrival process, while outgoing calls are made in
an exponentially distributed time. On finding the server unavailable (either
busy or temporarily broken down), incoming calls intrinsically join the virtual
orbit from which they re-attempt for service at exponentially distributed time
intervals. The system stability condition along with probability generating
functions for the joint queue length distribution of the number of calls in the
orbit and the state of the server are derived and evaluated numerically in the
context of mean system size, server availability, failure frequency and orbit
waiting time.
