.lli.<^rR.lCTS <■! I'll I. sVWTTA/ TECIIS'ICAI. I'JIT.RS IS.l 



nnuluilid that a phxsical rifirriuo system is essential, anil that a 

 mere siH-eilication of its plnsiial ()|H>ratinK chararteristirs is insuni- 

 eiciit. The inaile(|iiaeN' of the refireiice systems now in use is pointid 

 out. 



The conditions to bo aimed .it in the new reference s>stem are: 

 I — 'llie performance of the s>stcm and of its component parts mi^irt 

 be specitiai)le in terms of quantities admitting of definite physical 

 measurement; II — The performance of the reference system, under 

 specified njKTating and atmospheric conditions, must remain constant 

 with time; III — The reference system must be free from non-linear 

 distortion over the range of acoustic and electric amplitudes which 

 it must handle; IV' — The frequency response over the range of speech 

 frequencies must be as nearly uniform as possible. 



Uf the above, conditions I ami II are regarded as the most im- 

 jKtrtant. It is also proposed to build auxiliary reference systems 

 which will meet conditions I and II while falling short of III and IV. 

 These are needed for purposes of ready comparisons with the com- 

 mercial circuits commonly in use. 



