Dialing Habits of Telephone Customers

Following World War II the conversion of great quantities of manual telephone equipment to dial, and the addition of large numbers of new telephones, mostly dial, in the Bell System has directed increasing attention to those service problems peculiar to automatic operation. These problems concern chiefly the provision of adequate amounts of equipment to give satisfactory service at all times. One of the important factors affecting the amount of equipment needed is the action of the customers themselves when their calls are momentarily blocked due to these equipment shortages. The actions of subscribers whose calls are blocked due to a shortage of trunk equipment have been reported previously. This paper considers the behavior of subscribers, waiting to dial calls, when dial tone is delayed. During 1949, Bell Telephone Laboratories conducted a series of tests at the New York Telephone Company's Sterling-3 panel dial central office in Brooklyn, N. Y., with the object of increasing the knowledge available regarding subscribers' actions and their effects when dial tone is delayed. The following principal results were obtained from the Sterling-3 tests: 1. The relationship between the load carried by a group of line finders and the resultant dial tone delay. 2. Measures, by classes of service, of the magnitude of the general1 Charles Clos, "An Aspect of the Dialing Behavior of Subscribers and Its Effect on the Trunk Plant," Bell System Tech. J., 27, July 1948. 32 1 DIALING HABITS OF TELEPHONE CUSTOMERS 2 33 ized trunking formula's "j" factor describing the degree to which customers wait when dial tone is not immediate.