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BELL SYSTEM TECHNICAL JOURNAL 



sary to consider the econoniical limit of attenuation loss in each 

 repeater section, the degree of balance to be obtained between the 

 line impedances of the different sections and the corresponding bal- 

 ancing network impedances, and the proper transmission le\eis, as 

 well as the limited chf)icc of points where it would be practicable 

 to maintain these stations from an economy and maintenance force 

 standpoint. Fig. 3 shows the layout of through circuits on the south- 

 ern transcontinental line and a transmission level diagram of the 

 Chicago-Los Angeles telephone circuit, indicating the location and 

 spacing of repeater points, attenuation losses in the different sections 

 and amplification of repeaters. 



Impedance Characteristics. It has been practicable in the con- 

 struction of the new facilities to avoid long sections of intermediate 

 or entrance cable except at a few* points and in general, very smooth 

 impedance characteristics of the different repealer sections have been 

 obtained. At the points where appreciable lengths of cable could 

 not well be avoided, a special type of loading' has been designed 



leoo I60O eooo 

 rFEQi/fNcy 



1600 3200 



Fig. 4 — Impedance Characteristic 216 Mile Repeater Section Non-I-oa(lc<l Ui^ mil 

 Physical Circuit (Circuit Terminated to Appear as Infinite Line) 



for the piirpiisi' of raisini; the inipt'dance of llie cabk- ciicuils lo \allies 

 that match the impedance of the open wire at the carrier frequencies 

 as well as at voice frequencies. This loading also is of particular 

 benefit in reducing the attenuation loss at carrier freciiiencies which 

 in non-loaded cable may be com|)arativeIy high- 



The impedance characteristic of a typical repealer section 2H) 

 miles long is shown by the heav>' lines in Fig. 4. The circuit in this 

 case is terminated at the distant end by a network which makes it 



' Refer lo paper on "Carrier Current Telephony and Telegraphy," by Colpitis 

 am! HIarkwrll, prcvioush' noted. 



