STANDARD VOLUME INDICATOR AND REFERENCE LEVEL 119 



a reading of 80 per cent on an impulse of sine-wave as short as .025 

 second. 



The above characteristics were decided upon only after many tests 

 corroborated by field trials under actual working conditions. The 

 validity of the conclusions reached in the tests of earlier r-m-s volume 

 indicators was checked with respect to the new instrument by further 

 tests. 



Q 100 



0.4 0.5 Q.6 



TIME IN SECONDS 



Fig. 11 — Deflection of volume indicators to suddenly applied sine-wave. 



The question of whether the rectifier should be half-wave or full-wave 

 needs little discussion. The oscillogram of the speech wave shown 

 in Fig. 1 shows a very marked lack of symmetry. Evidently if a 

 volume indicator is to give the same reading no matter which way its 

 input is poled, a balanced full-wave rectifier is required. 



Throughout this paper, the term "r-m-s" has been used loosely to 

 describe the general type of instrument under consideration. Some 

 tests were made to determine how closely the new volume indicator 

 approximates this characteristic. 



