.tusTN.icis ()/• iiiii.i. sysriiM ri-ciixicii. i:irr.i<s ?m 



ri-.iilily compri'lu-iul tlu' ratios corrcsiioiuliiij; to ,m\- i^ivfii ihiiiiIxt of 

 imils. Sinri' it is di-siral)!*.- that every imil he hasid on a tiorinia! 

 system of notation, unless there is some \er\' important reason why 

 it should not, the 'IT hasiil on the decimal s\stem was chosen. Satis- 

 factory experience during the past year and a half is pointed to as ■ 

 showing the wisdom of having chosen the Tl'. 



.1 Siispfiisionfor SiipportiHi^ Delicate Instruments.^ A. I.. )( iiin^ki n. 

 Bell Telephone Laboratories, Incorporated, New N'nrk. A (Kscrip- 

 tion, with diagraiu, is given of a modified Julius suspension designed 

 especially to eliminate disturbances due to \ertical xibrations from 

 the building structure. The frame holding the instrument is sup[)orted 

 !)>• a system of tape-wound coil springs, which, because of the tightly 

 wound friction tape, damp out mechanical \il)rations. The frame 

 with its balancing weights, is heav>- (about 120 pounds), and so 

 proportionetl in mass that a twisting or tilting impulse, necessary- at 

 times in adjusting the instrument, disturbs its mo\ing system onh' in 

 a secondary degree. This is a second feature of this suspension. 

 Surprisingly efFecti\e kinetic insulation is achieved. Quaclrant 

 electrometers and a moving magnet gal\"anometer have remained 

 umlisturbed even when heavy trucks were passing on the street seven 

 fl(K>rs below. This type of suspension, developed some years ago 

 through the efforts of Mr. H. C. Harrison and Mr. J. P. Ma.xfield, 

 has been adapted for use throughout the Bel! TeleiilioTie Laboratories 

 in a variety of ways. 



Po'icer Amplifiers in Transatlantic Radio Telephony.'' A. A. Osw.m.d 

 and J. C. SntELLKNC. The paper describes the dc\eIopment of a 

 l.")0-kilowatt (output) radio frequenc\' amplifier installation built for 

 transatlantic telephone tests. The characteristics of the single- 

 sideband eliminated-carrier method of transmission are discussed 

 with particular reference to its bearing upon the design of the power 

 apparatus. A classification of amplifiers is proposed in which there 

 are three types distinguished from each other by the particular por- 

 tion of the tube characteristic used. The water-cooled tubes em- 

 ployed in these tests are briefly described, special consideration being 

 given to their use in a large installation. The system is then shown 

 in outline by means of a block diagram, the elements of which are sub- 

 sequently discussed in greater detail. The theory, electrical design. 

 and mechanical construction of the last two stages of the amplifier 

 are outlined, including the output and antenna circuits. Means em- 

 ployed to prevent spurious oscillations are described. The method 



•Journal Opt. Soc. of .^m.. Vol. X, No. 5, pp. 609-611, May, 102$. 

 * Proc. of I. R. E.. \ol. 1.5. page 313, June, 1925. 



