THE RING ARMATURE TELEPHONE RECEIVER 



12.^ 



Network Representation 



The representation of electro-acoustical transducers as electrical networks 

 has long been a useful tool.^^- ^^ Extensive use of this analogy has been made 

 in the development and design of the ring armature receiver. The saving of 

 time and increase in accuracy and completeness of analysis possible with 

 this technique is apparent when it is realized that a complete family of re- 

 sponse-frequency characteristics, showing the effects of variation of one or 

 more of the mechanical or acoustical constants of the instrument, can be 

 obtained by electrical measurements of voltage on an electrical network for 

 various settings of variable inductances, capacitances, or resistances which 

 simulate the mechanical or acoustical constants of interest. The amount of 

 work required to obtain the same information by building and testing me- 

 chanical and acoustical models is such that in many cases it would be im- 

 practical or impossible within a reasonable time interval. 



Fig. 11 — Block diagram network representation for receivers. 



A complete generalized representation of the ring armature receiver is 

 shown in Fig. 11 in block diagram form. Ze is the electrical impedance of the 

 instrument with all motion of the armature blocked mechanically. Z^ in- 

 cludes a mesh which simulates the effects of eddy currents in the metallic 

 structure of the instrument, r is the force factor, defined as the force applied 

 to the armature per unit of current flowing in the receiver winding. Zm is the 

 mechanical impedance of the mechanical and acoustical portion of the 

 receiver at the point of application of the force, F. The relationships in this 

 diagram are 



and 



Z = Ze + 



The term ^ is the motional impedance of the instrument. 



Zm 



""High Quality Recording and Reproducing of Music and Speech," J. P. Maxfield 

 and H. C. Harrison, Bdl System Technical Journal, July 1926 t> • . o«^ 



12-Theory of Magneto-Mechanical Systems as apphed to Telephone Receivers and 

 Similar Structures," R. L. VVegel, Am. Inst, of Elec. Eng., October 1921. 



