THE TR.tXSMISSlOX IXIT .IXP REVF.REXCE SYSTEMS 407 



rfprt>s».'jits :i gain of 3.01 units, and a (H)\ver ratio of 0.5 corrt-sponds 

 to a loss of H.Ol units. If the alH)vi' ratios were for current, tin; 

 lo>;aritluns wouKI Ik? nuiltipliofl h\ 20. Thus a current ratio of 2 

 (•orri's(M)n(ls to a gain of ().()2 units and a current ratio of 0..") corre- 

 s[X)nds to a loss of ().{)2 units. 



It will l)e noted that the T U is Inisi-d on the same ratio It)"' as 

 the series of preferred numbers which has Ijeen used in some Kuro()ean 

 countries and has Ikh^u proposed here as the basis for size standardiza- 

 tion in manufactured articles.- In common with this series, the T U 

 has the advantage that many of the whole numbers of units ccjrre- 

 spond approximately to easiK- remembered ratios ;us shown in tin- 

 following table. 



APPROXIMATE POWER RATIO 



It will be seen that the ratio for a gain of a given number of T U 

 is the reciprocal of the ratio for a loss of the same number of units. 

 Also for an increase of 3 in the number of units, the loss ratio is ap- 

 pro.ximately halved and the gain ratio doubled. If the approximate 

 loss ratios corresponding to I, 2 and 3 units are rememlx-red, the 

 others can be easily obtained. 



From this consideration of the properties of the transmission unit, 

 it is evident that there is much to commend its use in telephone 

 transmission work. Furthermore, since its advantages are not peculiar 

 to this work, such a unit may find applications in other fields. It is 

 now being used in some of the work on sound. 



•Size Standardization by Preferred Numbers, C. F. llirshfeld and C. M. Berry, 

 Mechanical Engineering, December, 1922. 



