On Tuesday, June 17, 2014 2:40:12 PM UTC-4, mrob...@att.net wrote:   
      
   > Around   
   > that time, improved materials and manufacturing started allowing for   
   > physically smaller capacitors that have a decent amount of energy   
   > storage.   
      
   Side note about capicitor size:  Landline telephone sets have always had a   
   capcitor to separate the 20 Hz ringing current from the 48V DC signal and talk   
   power.  Many years ago the capacitor to do this was so large that the ringer   
   unit required a box    
   separate from the telephone set.  In 1938 they reduced the size enough to fit   
   it all in a "combined" set (the WE 302 or AE 40).  Even then the capictor was   
   still the size of a hot dog.  In 1950 they reduced it again and placed it,   
   with other components,    
   into a roughly 1" cube (the classic WE 500 set).  Today, it's extremely tiny.   
      
   Train note:  The PATCO internal telephone exchange (a PAX) was located atop a   
   substation in Center Tower.  As a result, there was always a 60 cycle   
   background hum on their phone lines.  (This has been fixed).   
      
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