New criterion of telephone circuit performance

The paper proposes a new unit by which the overall capabilities of a telephone circuit can be defined. The upper limit of the scale by which the efficiency of the current is defined as that performance in which all frequencies are transmitted in the audible range free from distortion and having a speech level of 70 db above threshold zero is obtained by preventing all speech components reaching the listener at a level beyond threshold. Subdivisions of the scale are determined in terms of values of sound articulation.