A New Objective for Message Circuit Noise

Abstract

The reduction and control of noise on message circuits must be based on sound noise objectives. For many years the Bell System over‐all performance objective has been “26 dbrnc (20 dba) seldom to be exceeded at the telephone station set.” In this article the derivation of a more flexible and operationally feasible noise objective is presented. This objective specifies a limit of 20 dbrnc not to be exceeded on subscriber loops, and stipulates various distributions for noise originating beyond class 5 offices on built‐up connections. The objective is such as to provide Bell System customers with a noise grade of service ranging from 99 per cent good or better on short connections to 90 per cent good or better on intercontinental connections spanning distances up to halfway around the world.

Spurious Signal Criteria for Voiceband Telephone Equipment

“…The maximum total noise objective for voiceband service is 20 dBrnC. 9 Half this noise is allocated to crosstalk interference; therefore, Ν = 17 dBrnC. The maximum longitudinal signal voltage that may be introduced by a voiceband terminal at any given frequency, (f), is:…”

Some Transmission Characteristics of Bell System Toll Connections

“…1 The results of this survey found an important application in the setting of new over-all objectives for background noise. 2 A similar survey was undertaken in the summer of 1966. It is our purpose to describe this connection survey and to give its results.…”