Development and Application of Loading for Telephone Circuits

A review of t h e a r t of loading telephone circuits as practised in t h e United S t a t e s . T h e i n t r o d u c t o r y section briefly reviews t h e t h e o r y of coil loading, a n d s u m m a r i z e s t h e principal characteristics of t h e first commercial s t a n d a r d loading coils a n d loading systems, t h e r e b y serving as a background for t h e description of t h e various i m p r o v e m e n t s of o u t s t a n d i n g i m p o r t a n c e which h a v e been m a d e in t h e loading coils a n d loading s y s t e m s d u r i n g t h e past fifteen years to meet t h e new or c h a n g i n g r e q u i r e m e n t s in t h e rapidly a d v a n c i n g c o m m u n i c a t i o n a r t . T h e s e m a j o r i m p r o v e m e n t s are described in detail under t h e a p p r o p r i a t e headings (1) P h a n t o m G r o u p Loading, (2) L o a d i n g for R e p e a t e r e d Circuits, (3) Incidental Cables in Open Wire Lines, (4) Cross-talk, (5) T e l e g r a p h y over Loaded Telephone Circuits, (6) Loading for E x c h a n g e Area Cables, a n d (7) S u b m a r i n e Cables. T h e discussion of these v a r i o u s d e v e l o p m e n t s sets forth t h e relations between t h e loading f e a t u r e s a n d t h e associated phases of telephone d e v e l o p m e n t , such as t h e cables, repeaters, telegraph working, a n d carrier telephone a n d telegraph systems. T h e concluding p a r t of t h e p a p e r gives some general statistics regarding t h e e x t e n t of t h e commercial application of loading in t h e United States, a n d a brief s t a t e m e n t indicative of t h e large economic i m p o r t a n c e of loading to t h e telephone using public.