480 BELL SYSTEM TECHNICAL JOURNAL 



The degree to which maintenance may affect performance and the 

 necessity for automatic equipment are shown by data obtained in the 

 field. Apparatus and systems which enable the operating staff to 

 meet modern frequency stability requirements by monitoring the 

 emitted carrier are also described. 



Tape Armored Telephone Toll Cable.^ C. W. Nystrom. Toll 

 cables buried directly in the earth are coming into increased use. 

 Such cables are not installed in the usual clay conduit but are protected 

 by layers of paper, jute, and steel tapes. Complete equipment for 

 laying this cable has been developed. 



Some Effects of Topography and Ground on Short-Wave Reception.^ 

 R. K. Potter and H. T. Friis. This paper contains some results 

 of an experimental study of the effects which ground and ground 

 irregularities have upon short-wave signal reception. The results 

 illustrate the signal strength advantage to be gained in the selection of 

 suitable ground or topographical conditions and show the influence 

 of antenna types, and vertical angle of signal arrival, upon such an 

 advantage. Although the tests were confined to reception, the con- 

 clusions are probably applicable in general to the case of transmission. 

 The agreement between measurement data and theory seems to justify 

 the application of plane wave optical theory to the calculation of 

 vertical plane directivity of antennas. Such an application suggests, 

 according to the data obtained, that signals from South America are 

 normally received at much lower vertical angles than those from 

 England. 



Western Electric Noiseless Recording^ H. C. Silent and J. G. 

 Frayne. The Western Electric method of noiseless recording with 

 the light valve is described. The general principles are discussed, 

 the circuit diagram is explained, and the method of adjusting the 

 device for service described. The photographic characteristics of 

 film are considered, and their application in noiseless recording is 

 shown in some detail. 



The Acoustics of Large Auditoriums.^ S. K. Wolf. Extremely 

 large auditoriums present acoustical difficulties which do not readily 

 yield to the customary methods of analysis and correction. This is 

 illustrated by measurements of the time of reverberation, made in 



^Electrical Engineering, March, 1932. 

 « Proc. I. R. E., April, 1932. 

 ' Jour. S. M. P. E., May, 1932. 

 8 Joiir. S. M. P. E., April, 1932. 



