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BELL SYSTEM TECHNICAL JOURNAL 



Characteristics of Improved Cable Loading Systems. The principal 

 electrical features of the H-44-2o and H-174-63 phantom group 

 loading systems which have been developed primarily for use on long 

 repeatered cables are given in Table X. Corresponding details of 

 the older standard loading system developed for non-repeatered 

 cables are also included in this table. Typical attenuation-frequency 

 curves of the old and new loading systems are given in Fig. 10. 



0.87 



500 1000 1500 2000 2500 3000 3500 

 FREQUENCY- CYCLES 



Fig. 10 — Attenuation-frequency characteristics of toll cable loading 



In the following discussion of detailed characteristics, the various 

 phantom group loading systems will be referred to in terms of recently 

 standardized designations w'hich include a letter to symbolize the 

 coil spacing, in combination with tW'O numbers which correspond 

 with the efifective coil inductance \alues in milhenrys, the first num- 

 ber referring to the side circuit coils and the second number to the 

 phantom coils. The individual side circuit or phantom circuit loading 

 systems have designations which include a letter to s>iTiboIize the 

 coil spacing, coupled with the inductance value of the loading coils in 

 milhenrys, and having a letter suffix "S" or "P" indicating the type 

 of circuit, side or phantom. 



The fundamental differences between the new and the old loading 

 systems are with respect to velocity of wave propagation and cut-off 

 frequency, these changes having been made in accordance with the 

 preceding discussion primarily for the purpose of reducing echo 

 effects and transient distortion. F'or reasons of plant economy and 



