ABSTRACTS 161 



A Coil-Neutralized Vacumn-Tube Amplifier at Very High Frequencies.^ 

 R. J. KiRCHER. This paper describes a two-stage single-side coil-neutralized 

 amplifier employing an experimental triode operating in the vicinity of 140 

 megacycles. Circuit features are described and typical operating conditions 

 are indicated. Typical distortion characteristics at low-power levels are 

 also included. 



Fundamental Theory of Servomechanisms} LeRoy A. MacColl. The 

 use of servomechanisms and related devices for automatic control and 

 regulation is ver\' old, dating back to the latter part of the eighteenth 

 century. However, it is only recently, approximately since the beginning 

 of the war, that it has been recognized that these devices are essentially 

 feedback amplifiers in a mechanical, or partly mechanical, form. From 

 the recognition of this fact it follows that the highly developed theory of 

 electrical feedback amplifiers can be applied at once to servomechanisms 

 and similar devices. 



This book, which was originally intended to be a National Defense Re- 

 search Committee report, is an introduction to the theor>' of linear servo- 

 mechanisms, considered as a special application of the general theory of 

 feedback amplifiers. The steady-state theory of the systems is taken as 

 fundamental, and the various problems concerning the stabiUty and per- 

 formance of the systems are discussed in terms of it. In the several chap- 

 ters a variety of types of linear servomechanisms are considered. A brief 

 discussion of one simple non-linear servomechanism is given in the Ap- 

 pendix. 



Corrosion Protection for Transcontinental Cable West of Salt Lake City, 

 Utah.^ T. J. Maitland. This paper discusses the problems involved in 

 maintaining the effectiveness of the thermoplastic covering provided on 

 buried toll cables for installation in areas where corrosion is anticipated. 

 It also describes the method used to obtain the required supplemental 

 electrical drainage for the Transcontinental Cables across the Great Salt 

 Desert west of Salt Lake City where the low earth resistivity and high 

 concentration of alkali salts preclude the use of rectifiers connected between 

 cable sheath and a made ground generally employed for drainage purposes. 

 Such installations would result in negative potentials between cable and 

 earth of sufficient magnitude to create conditions conducive to cathodic 

 corrosion of the lead sheath in the presence of an alkali salt electrolyte. 



To provide electrical drainage without incurring these excessive negative 

 potentials a method was developed utilizing the normal potential difference 

 between zinc and lead as the source of drainage current. Twenty-four 

 pound zinc bars of commercially available zinc, 99 per cent pure, were in- 

 stalled directly in the ground a short distance from the cables at 12-mile 



*Proc. I. R. E., December, 1945. 



6 Published by D. Van Nostrand Company, Inc., New York, N. Y., 1945. 



' Corrosion, June 1945. 



