A new objective for message circuit noise

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.