124 



THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1951 



In studying the performance of an instrument the three elements in the 

 above block diagram, Ze , r, and Zm are considered separately, and a difTer- 



MEMBRANE-DIAPHRAGM GRID-MEMBRANE EAR COUPLING ^CAP GRID HOLES, 



CHAMBER, Sm -- CHAMBER, Sq CHAMBER, Sc /^ Rg^g 



X / 



membrane, ^ 



RmMm 



DIAPHRAGM, - 

 SdMq Rd 



AIR GAP, RaMa 



COIL CHAMBER; — 



Sa 



back chamber,- 

 Sb 



HOLE, RhMh" 



ACOUSTIC RESISTANCE - 

 ELEMENT, Rx Mx 



HANDSET HOUSING CHAMBER 



Sx 



2m 



So Rd Md 



-|( — v\A^ — nm^ 



.Ml 



•Rh 



M» 



Rg Mg 



Sm zi=Z^G 



:i:SA 



Ra 



Ma 



:4^Sb 



l-AAA^^Wy^ ^AAr^^W^ 



:Sc 



^Sx 



Rx Mx 



Fig. 12. — Zm. Equivalent network of mechanical and acoustical elements of ring arma- 

 ture receiver. 



ent type of analysis applied to each. These three elements and their analyses 

 and uses will be discussed separately below : 



(a) Mechanical and Acoustical Elements 



The element of the block diagram represented by Zm is the portion of the 

 network representation of most use in the development and design of re- 

 peivers. Figure 12 shows an expansion of Zm into an equivalent electrical 



