Unsuccessful calls in PBX-human factor considerations

This paper presents an approach to the use of traffic measurements data for advance conclusions about the quality of service in the telephone traffic. Unsuccessful calls in an optimally structured private branch exchange (PBX) are considered as faults, with direct implication to the quality of service and degree of users´ satisfaction. The observations are focused on the local calls only. A short history, common facilities of calls and additional services are described as well as human behavior during call managing. Particular attention is given to finding the reasons for low call completion. The data for this analysis have been collected during four months of real time traffic measurements. The interval of traffic measurements covered a working day. The results of traffic measurements show very unstable traffic during that period i.e. high fluctuation of traffic between measurement days.