A study of network performance and customer behavior during direct-distance-dialing call attempts in the U.S.A.

A survey was conducted throughout the Bell System in October 1974 to gather detailed information about Direct-Distance-Dialing call attempts. The dispositions, setup times, and customer abandonment times associated with DDD attempts are discussed in detail in this article to provide network performance and customer behavior characteristics to network planners and administrators and to designers of equipment and systems which use, and interact with, the telephone network. It is shown that both network performance and customer behavior affect the call dispositions and the total call setup time; however, customer-dependent failures to complete account for 85 percent of all failures, and customer-determined components of the call setup time make up 71 percent of the total setup time. It is found that traffic composition in terms of the relative mix of business and residential originations exerts a strong influence on call dispositions. Network performance affects the probability of equipment blockages and failures and the interval from end of dialing to receipt of a network response. These are both found to depend on calling distance, while the latter is also affected by the types of originating and terminating local switching.