STANDARD VOLUME INDICATOR AND REFERENCE LEVEL 123 



indicator service. It is evident, however, that the scale card, which 

 contains all kinds of identification data, is entirely too confusing for 

 quick, accurate observations as the needle swings rapidly back and 

 forth across the scale. 



The scale shown in Fig. 15 has the merit of simplicity and easy 

 readability. It is, however, somewhat limited in the decibel range 

 appearing on the scale. 



Fig. 14 — Scale on type 586 power level indicator. 



New Scale 



Both vu ^ markings and markings proportional to voltage are in- 

 corporated in the new instrument scale. The need for the former is 

 obvious, but the philosophy which leads to the inclusion of the latter 

 requires an explanation. 



It is evident, assuming a linear system, that the voltage scale is 

 directly proportional to percentage modulation of a radio transmitter 

 upon which the program is finally impressed. If the system is ad- 

 justed for complete modulation for a deflection to the 100 per cent 



' Defined later. 



