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BELL SYSTEM TECHNICAL JOURNAL 



background. The decibel divisions and associated numerals are in 

 red and considerably less conspicuous than the main scale. 



However, the to 60 scale, which is used on both of the instruments 

 shown in Figs. 12 and 13, is an arbitrary one bearing no simple relation 

 to the electrical quantity being measured. Because of this, some of 

 the non-technical persons concerned with program production are 

 prone to request that a certain "effect" which they desire to transmit 

 at a louder-than-normal level be permitted to swing the indicating 



Fig. 13 — Scale on 21 type volume indicator. 



needle beyond the normal reference point of "30" on the scale. It is 

 not evident to them from the instrument scale that the normal reading 

 of "30" corresponds to maximum " undistorted " output of the system. 

 The scale shown in Fig. 14, on the other hand, was primarily in- 

 tended for steady-state and not volume level measurement purposes. 

 Consequently, this scale has little, if anything, to commend it for 

 program monitoring use. Nevertheless, the simplicity and the fine 

 electrical features of this type of instrument, together with its rela- 

 tively reasonable cost, have resulted in its general application to volume 



