526 



BELI. SYSTEM TECIISICAI. JOCRNAL 



repeaters; that is, devices for aniplif\ing feeble teleiihone eurrents, 

 passini; in either direction o\er a telephone cirniit. \viiht)iit apprecialile 

 distortion. Tlie most successful repeaters of tin's l\pe. as \()ii nia\ 

 know, u^e as the ainplif\injj element the \acmun iu!)e, alihouiih 

 the tube itself is but a \ery small part of the apparatus required for the 

 successful operation of the telephone repeater, antl man\- interesting 



Fig. 2 — Open wire toll liiu' 



engineering pr()i>k'ni> had tii i)c s(>l\ i-<l in piov idin;.; a i(inipi(.'lc rc|)ealei". 

 A full discussion of this \ery imi^ortanl and interesting de\elopment 

 is gi\en in a paper by Mr. Gherardi and Dr. Jewett, jiublished in the 

 Transactions of the A. I. K. E. for 191!). 



The loll cable de\elopnient, based on the use of repeaters as outlined 

 above and many other technical impro\ements, now makes it possible 

 to gi\'e satisfactors' service between Chicago and New York and inter- 

 mediate jioints o\er toll cable circuits of such small gauge that dose 

 to liOO circuits can be included in a single sheath of 25 s" in diaTneter. 

 The same number of circuits would reciuire four or the \'cr>' hea\il\- 

 built pole lines of open wire construction such as is shown in Fig. 2. 



The construction of the Chicago-New ^'o^k cable was started in 

 I'.IIS and will be completed this year. As shown in Fig. 1, the cable 



