858 BELL SYSTEM TECHNICAL JOURNAL 



The power circuit analyzer is designed to measure harmonic voltages 

 in the frequency range from 75 to 3000 cycles and over a voltage 

 range from 0.5 millivolt to 50 volts. The telephone circuit analyzer 

 operates over the same frequency range and measures harmonic 

 currents as low as 0.05 microampere and voltages as small as 0.005 

 millivolt. Both analyzers are adapted to measure small harmonic 

 voltages and currents in the presence of the fundamental component 

 and other harmonics relatively large in magnitude. 



A number of devices are described which have been adopted for 

 eliminating various sources of error. The paper presents in detail 

 the characteristics of both instruments with respect to selectivity, 

 sensitivity, linearity, balance of input with respect to ground, genera- 

 tion of harmonics, and susceptiveness to stray fields. 



Solution to a Problem in Diffusion in Employing a Non-Orthogonal 

 Sine Series}^ R. L, Peek, Jr. In this paper there are developed 

 the equations applicable to diffusion through a membrane between a 

 chamber in which a constant pressure of the diffusing material is 

 maintained and a second closed chamber, initially evacuated, into 

 which the material diffuses. Assuming Pick's law to apply, a solution 

 is obtained in the form of an infinite series of a type similar to those 

 applying to other problems in diffusion. The sine series to which the 

 solution reduces at zero time is non-orthogonal, but it is shown that 

 by a modification of Pourier's method the coefficients of the terms 

 may be directly determined. There is included a proof of the con- 

 vergence of the series considered. 



Telephone Transmission Networks}^ Types and Problems of Design. 

 T. E. Shea and C. E. Lane. In this paper is given a brief resume 

 of the nature of telephonic signals showing how the qualities of wave 

 composition which distinguish signals from other electrical waves set 

 the requirements on networks and provide a basis for their design. 

 The principal functions of wave filters, equalizers, telephone trans- 

 formers, line balancing networks, and artificial lines are outlined. 

 In order that these networks may be used in conjunction with other 

 apparatus in the telephone system they must provide efficient trans- 

 mission, low distortion, good impedance balance, stoppage of longi- 

 tudinal currents, stable characteristics with current variations, low 

 external coupling, and low reflection coefficient. In addition to these 



^'^ Annals of Math., 2d Series, Vol. 30, April, 1929, pp. 265-269. 



" Presented at the Regional Meeting of the South West District No. 7, of the 

 A. I. E. E., Dallas, Texas, May 7-9, 1929. Abridgment in A. I. E. E. Journal of 

 August, 1929, pp. 624-628. 



