ABSTRACTS OF TECHNICAL ARTICLES 649 



Rectilinear Electron Flow in Beams. ^ J. R. Pierce. Electrodes are 

 devised by means of which rectilinear electron flow according to well- 

 known space charge equations can be realized in beams surrounded by 

 charge-free space. It is shown how these electrodes can be used in the 

 design of electron guns having desirable characteristics. 



High-Gain Amplifier for 150 Megacycles.^ G. Rodwin and L. M. 

 Klenk. An ultra-high-frequency amplifying system is described 

 which operates at about 150 megacycles with an over-all gain of 114 

 decibels and transmitted band of over 2 megacycles. An output power 

 of 2.5 watts is available with a signal-to-distortion ratio of 60 decibels. 

 By a frequency-shifting modulator in the amplifier chain the input 

 and output are made to differ by 10 megacycles. A filter-type circuit 

 is used as the interstage coupling to give the necessary band width. 



Room Noise at Subscribers' Telephone Locations.'' D. F. Seacord. 

 The effect of room noise on the ability to hear speech is roughly 

 equivalent to a partial deafening of the listener; hence the study of 

 room noise conditions at telephone locations is of considerable interest 

 to the telephone engineer since these conditions have an important 

 bearing on the degree of satisfaction with which speech is received over 

 a telephone connection. As a consequence, various studies of room 

 noise have been made from time to time and information of increasing 

 value has been obtained over a period of years with the development of 

 improved measuring equipment and technique. This paper is based on 

 the results of recent room noise surveys carried out in the Bell System 

 and gives a broad picture of the magnitude of room noise at subscribers' 

 telephone locations under present-day conditions. The data presented 

 are a part of the information required in the work of devising and 

 applying methods for taking into account the effects of room noise on 

 telephone transmission in the design of the telephone plant. 



Temperature Effects in Secondary Emission.^ D. E. Wooldridge. 

 Measurements have been made on the effects of temperature changes on 

 the emission of secondary electrons from iron, nickel, cobalt, and 

 molybdenum. Abrupt changes of one or two per cent were observed 

 to accompany the a — 7 transition of iron, while the hexagonal to face- 

 centered cubic transformation of cobalt was accompanied by a change 

 in secondary emission of only about 0.4 per cent. The magnetic trans- 



' Jour. Applied Physics, August 1940. 

 «Proc. /. R. E., June 1940. 

 ^ Jour. Acous. Soc. Atner., Julv 1940. 

 « Phys. Rev., August 15, 1940." 



