The Transmission Performance of Bell System Toll Connecting Trunks

The Bell System telephone network consists of a hierarchy of transmission facilities available for connecting one subscriber to another. These include the loops from the subscribers to their local telephone office, toll connecting trunks from the local to the toll office, and intertoll trunks between these toll offices. Clearly, the transmission performance of a toll connection is affected by each part of this built-up connection. Overall measures of performance have been reported in previous connection surveys 1 ' 2 and there has been a recently completed 1969-70 Connection Survey. 3 - 5 There is a concurrent need for detailed knowledge of the specific parts of toll connections. This information finds important applications in the setting of trunk objectives for the. various transmission parameters, and in the effort to simulate, on a computer, a model of the Bell System transmission network. To this end, this paper reports various population estimates of the transmission performance of toll connecting trunks, based on a systemwide survey undertaken in 1966. Individual portions of this information have been used separately, and this paper serves to bring all the results together in a single document. To the author's knowledge, these data represent 2741