Artalejo Rodríguez, Jesús ManuelFalin, Guennadi I.2023-06-202023-06-201996-120894-069X10.1002/(SICI)1520-6750(199612)43:8<1147::AID-NAV6>3.0.CO;2-Ehttps://hdl.handle.net/20.500.14352/57486The first author acknowledges support from University Complutense of Madrid through Grant No. PR161/93-4777. We also thank the referees for their comments, which helped us to improve the clarity of the article.In teletraffic applications of retrial queues only the service zone is observable. Another part of a retrial queue, the orbit, which represents the delay before repeated attempts to get service, cannot be observed. Thus, it is very important to get general results about behavior of the orbit. We investigate two characteristics of the orbit, namely, the orbit busy period and the orbit idle period, which seem to be very useful from this point of view.spajournal articlehttp://onlinelibrary.wiley.com/doi/10.1002/(SICI)1520-6750(199612)43:8%3C1147::AID-NAV6%3E3.0.CO;2-E/pdfhttp://onlinelibrary.wiley.com/restricted access519.8Investigación operativa (Matemáticas)1207 Investigación Operativa