lllliOKY Ol' Jll/i I loin. IXC I r.l.l-.I'llONE 49 



When the transmitter and receiver are C()iii)Ie(l by the air in an 

 open room (he I)ehavi()r is somewhat similar to the case just solved. 

 The size and shape of the room as well as the disposition of articles 

 of furniture will all influence the intensity and freciuency of howling. 

 In general when the lw(j instruments are mo\ed apart the fre(iuency 

 will go up and down similar to that when tiiey are coupled by a tube. 



NOMENCLATURE 



T Transmitter Resistance. 



R Impedance looking away from Transmitter Terminals. 



Zfi Impedance of Receiver. 



Zd Damped Impedance of Receiver. 



e Electromotive Force Created in tlie Transmitter. 



i Alternating Current in the Transmitter Branch. 



M Unilateral Mutual Impedance between Receiver Current and Transmitter 

 e.m.f. 



Fji Force on Receiver Diaphragm. 



Ft Force on Transmitter Diaphragm. 



Sr Stiffness Factor of Receiver Diaphragm. 



^T- .Stiffness Factor of Transmitter Diaphragm. 



y Receiver Diaphragm Displacement. 



z Transmitter Diaphragm Displacem?nt. 



m Mass of Diaphragm. 



r Mechanical Resistance of Diaphragm. 



s Elastic Constant of Diaphragm. 



/ Frequency. 



CO Itt times Frequency. 



Z Force Factor of Receiver. 



5 Loaded Stiffness of Receiver Diaphragm. 



/ Direct Current Supplied to Transmitter. 



V DC Voltage Drop across Transmitter Terminals. 



h Modulation Factor of the Transmitter. 



.Y Mechanical Force on Receiver Diaphragm for Case I. 



E Electromotive Force of Supply Battery. 



k Resistance in Line for Case I. 



K Capacity of Condenser. 



Vji Volume of Air in Front of [Receiver Diaphragm. 



Vf Volume of Air in Front of Transmitter Diaphragm. 



Qn Effective Area of Receiver Diaphragm. 



Qt Effective Area of Transmitter Diaphragm. 



p Air Pressure. 



7 Adiabatic Constant. 



4> Velocity of Potential. 



a Velocity of Sound in Air. 



X Distance Along Connecting Tube. 



p Density of Air. 



^R Displacement of Air Particle at Receiver End of Tube. 



f r Displacement of Air^Particle at Transmitter End of Tube. 



