506 BELL SYSTEM TECHNICAL JOURNAL 



ance which equals the nominal characteristic impedance in the trans- 

 mission band, uniform response in the terminating resistance is ob- 

 tained over the entire band. 



Detailed Analysis of Mechanical and Electrical Analogs ^ 



Before going on with a detailed treatment of the electrical analogs 

 of the mechanical structures used in the problem of phonographic re- 

 production, a list of the corresponding quantities used in the two sys- 

 tems will be given, together with the symbols employed. 



Mechanical Electrical 



Force = F (dynes) Voltage = E (volts) 



Velocity = v (cm. /sec.) Current = i (amperes) 



Displacement = 5 (cm.) Charge = q (coulombs) 



Impedance = z (dyne sec. /cm.) Impedance = Z (ohms) 



or mechanical ohms 



Resistance = r (dyne sec. /cm.) Resistance = R (ohms) 



Reactance = x (dyne sec. /cm.) Reactance = A' (ohms) 



Mass = m (gms.) Inductance = L (henries) 



Compliance = c (cm./dyne)^ Capacity = C (farads) 



Fig. 10 — This figure shows an electromagnetic recorder complete except for the bot- 

 tom of the case 



In addition to the above certain other quantities such as angular 

 displacement, pressure and impedance per unit area, and a few others 

 which have no direct electrical analog will be used. These quantities, 



' The authors wish to express their appreciation to Mr. E. L. Norton for his courtesy 

 in working out the mathematics of the mechanical and electrical analogs which are 

 shown in this paper. 



** H. W. Nichols, "Theory of Variable Dynamical Electrical Systems," Phys. Rev. 

 Vol. 10, 1917. 



