We study the stability of a single-server retrial queueing system
with constant retrial rate and general input and service processes.
In such system the external (primary) arrivals follow a renewal input with rate λ. The system also has service times with rate μ. If a new customer finds all servers busy and the buffer
full, it joins an infinite-capacity virtual buffer (or \textit{orbit}). An orbital (secondary) customer attempts to rejoin the primary queue after an exponentially distributed time with rate μ0