1058 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1954 



connecting plant where, from a practical standpoint, certain features of 

 the h\'brid-coil repeater are not needed. For example, more than 10 

 db gain is rarely required, and unequal gains in opposite directions would 

 not ordinarily he useful. Besides, methods of signaling requiring a 4-wire 

 split of the repeater are not utilized on exchange area trunks. 



In addition to its important new characteristics, the series-shunt 

 combination retains the desirable features of the earlier series repeater, 

 i.e., it preserves dc continuity, it is simple in design and it is easy to 

 install and maintain. If properly engineered and installed on circuits of 

 reasonably uniform impedance, the new repeatei's can be operated in 

 tandem, do not have serious reactions on return loss, and are capable of 

 reducing the losses of the trunks to about the same values as hybrid-type 

 repeaters. 



SCOPE OF APPLICATION OF THE NEW REPEATER 



With the reduction of the return loss reaction of the earher form of 

 negative impedance repeater, the extent of application of the new E23 

 repeater becomes largely a matter of economics. In the telephone trunk 

 plant, there are generally three gauges of conductors available for trunk 

 use, namely, 19, 22 and 24. The larger gauges, utilizing more copper and 

 requiring more conduit space, naturall}' cost more than the smaller 



CD 4 



10 12 14 16 



TRUNK LENGTH IN MILES 



Fig. 1 — Illustrative field of use; interoffice trunks. 



