The calculation of articulation for effective rating of telephone circuits

It has long been recognized that the design of telephone circuits on a purely volume or loudness basis is inadequate. The volume basis of design goes back to the time when attenuation was the principal problem of long-distance transmission. Now line attenuation no longer limits the distance over which transmission can be effected and communication engineers are able to concentrate on the problem involved in providing circuits to give good grade of transmission from every point of view. New methods are replacing the volume methods, and the new methods must take into consideration, in addition to volume, a number of other features affecting the quality of transmission. As is well known, the method that is being substituted is based upon service observations of the frequency with which subscribers have to make repetitions in order to convey their ideas to the listener. The paper gives a summary of fundamental ideas and describes an articulation calculator. Questions such as room noise and line noise, transmitter and receiver characteristics, non-linear distortion, the experimental measurement of articulation and crew calibration, are discussed. Tables of results accompany the paper and these are discussed in a final section