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Page 28
Projection Engineering, November, 1930
SUPER-DAVOHM
Wire Wound Precision Resistors
Type BLT
mm
Type BWE
Super-Da,vohms are known and used in the entire world. Instrument manufacturers have adopted the Super-Davohm as an integral part of their assembled unit. Universities, electrical, physical, instrument and radio research laboratories are using Super-Davohms as laboratory standards because of their excellent characteristics.
Recommended for: Television Amplifiers, Telephone Equipment, Sound Picture Equipment, Fire Alarm Equipment, Voltmeter Multipliers, Resistance Amplifiers. Electrical Instruments, Laboratory Standard Resistors, Attenuators and Fading Controls.
(ASIUAfciSlZE)
Send Us Your Resistor Specifications Samples on Request
THE DAVEN COMPANY
RESISTOR SPECIALISTS
General Office and Factory 158-160 Summit Street, Newark, New Jersey
a modern book
on a modern
subject
Photocells
and their
Application
By
V. K. Zworykin
and
E. D. Wilson
Research Engineers, Westinghouse
Research Laboratories
Presents a comprehensive discussion of the theory of radiation and the photoemissive effect, the methods of preparing photocells, the various types of cells. The latter half of the book is devoted to a modern treatment of the manifold applications of photocells — their use in sound movies, in facsimile transmission, in television, and many others of the greatest importance. The book is concluded with a glimpse into the future
of photocells, in
ON APPROVAL COUPON
JOHN WILEY and SONS, INC., 440 Fourth Ave., New York
Gentlemen: Kindly send me for free examination Zworykin' s "Photocells." I agree to remit the price of the book ($2.50) within ten days after its receipt or return it postpaid.
feme . Address
Position or Beference.
dicating the trend of advancement
and improvement.
209 pages 5% by »Yz
$2.50
PE 11-30 I
AMERICAN 2 BUTTON
MICROPHONE
For sound recording, studio, public address system or sound research. Uniform response curve flat from 30 to 7000 cycles. No carbon hiss. Capacity 40 mills on each button. Wgt. Zyz lbs.
List $75.00
SPECIAL
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BASS CAMERA CO.
179 W. Madison St. Chicago, 111.
For Powers, Simplex and all other projectors equipped for sound.
&5vz>$.
Used by the S. Army Motion Picture Service.
The Clayton Even Tension Take-up assures absolute freedom from flutter. It takes up any amount of film evenly. It will take up with any size reel hubs. It prevents excessive wear on the lower take-up sprocket and shaft. It stops the opening of film splices and prevents excessive wear on the film.
Write for price and further information.
Joseph Clayton
9430 Forty-Sixth Ave. Elmhurst, L. I., N. Y.