Developments in the Application of Articulation Testing 



By T. G. CASTNER and C. W. CARTER, JR. 



The first part of this paper discusses the control and measurement of 

 variable factors involved in testing telephone circuits by the articulation 

 method and the simulation of the testing conditions in the laboratory to 

 those of actual use; the second part describes the auxiliary apparatus by 

 which these controls and measurements are efTected. This apparatus in- 

 cludes a caller's control circuit, by which the caller's speech intensity may be 

 measured and regulated independently of the circuit tested; a switching sys- 

 tem which automatically reverses the direction of transmission between test 

 sentences; devices for automatic and uniform agitation of carbon button 

 transmitters; equipment for automatic measurement of the magnitude of 

 the speech and noise waves on the circuits tested; phonographic sources of 

 line and room noise; and a control board at which circuit elements and 

 conditions can be changed and measured quickly. 



In addition, the time required to carry out a program of tests has been 

 materially reduced by the use of equipment which analyzes the articulation 

 data automatically and provides the test results in typewritten form im- 

 mediately after each list is called. 



Introduction 



ARTICULATION tests have been used for many years as one of a 

 number of laboratory methods of measuring the performance of 

 telephone circuits. The continued application of this method to 

 comprehensive programs of laboratory tests has emphasized the im- 

 portance of reducing the time required to obtain results of the desired 

 precision, and has led to the development of methods for accomplishing 

 this. By carrying to further refinement the control and measurement 

 of certain factors which have caused variations in the results, and by 

 the systematic use of certain modifications in the testing routine, the 

 precision of the tests has been increased with no increase in testing 

 time. In addition, the development of automatic equipment for 

 recording and analyzing the data, so that the results of the test are 

 immediately available in the form of a typewritten record, has reduced 

 by half the time required for carrying out a program of tests. At the 

 same time a number of features have been introduced to improve the 

 simulation of the testing conditions to those of actual service. 



In the present paper it is proposed first to discuss the objectives 

 which it has seemed desirable to reach and the methods which have 

 been adopted for doing so. The auxiliary equipment which is used 

 in articulation testing will be described in some detail in the second 

 part. 



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