﻿Variable 
  Frequency 
  Alternating 
  Currents. 
  485 
  

  

  condenser. 
  The 
  single 
  action 
  circuit 
  has 
  proved 
  o£ 
  value 
  

   for 
  telephonic 
  purposes. 
  

  

  Double 
  Action 
  Circuit. 
  — 
  The 
  double 
  action 
  circuit 
  previously 
  

   referred 
  to 
  is 
  illustrated 
  in 
  fig. 
  8. 
  

  

  This 
  circuit, 
  unlike 
  the 
  single 
  action 
  one, 
  gives 
  a 
  pronounced 
  

   oscillation 
  on 
  the 
  make 
  contact, 
  as 
  well 
  as 
  on 
  the 
  break. 
  

  

  On 
  referring 
  back 
  to 
  fig. 
  6 
  it 
  will 
  be 
  seen 
  that 
  no 
  oscil- 
  

   lation 
  can 
  occur 
  on 
  the 
  make 
  contact 
  as 
  the 
  battery 
  short- 
  

   circuits 
  the 
  oscillating 
  circuit 
  during 
  that 
  period. 
  

  

  By 
  introducing 
  resistance 
  into 
  the 
  battery 
  circuit, 
  however, 
  

   an 
  oscillation 
  on 
  the 
  make 
  contact 
  can 
  be 
  obtained 
  in 
  addition 
  

   to 
  the 
  break 
  oscillation. 
  This 
  oscillation 
  is 
  of 
  the 
  frequency 
  

   of 
  the 
  main 
  oscillating 
  circuit. 
  

  

  Fig. 
  8. 
  — 
  Double 
  Action 
  Circuit. 
  

  

  H 
  

  

  fTJ 
  

  

  fik 
  

  

  Although 
  the 
  results 
  might 
  have 
  been 
  predicted 
  theoreti- 
  

   cally, 
  the 
  following 
  series 
  of 
  oscillograms 
  (PL 
  XVIII. 
  fig. 
  9) 
  

   are 
  inserted 
  as 
  they 
  show 
  in 
  a 
  rather 
  interesting 
  manner 
  

   the 
  effect 
  of 
  insertion 
  of 
  resistance. 
  

  

  This 
  series 
  shows 
  the 
  variations 
  obtained 
  in 
  the 
  make 
  

   contact 
  oscillations 
  in 
  a 
  circuit 
  as 
  shown 
  in 
  fig. 
  6, 
  when 
  the 
  

   resistance 
  in 
  series 
  with 
  the 
  battery 
  (which 
  is 
  of 
  negligible 
  

   internal 
  resistance) 
  is 
  varied 
  from 
  4000 
  to 
  ohms. 
  

  

  The 
  make 
  oscillation 
  is 
  most 
  evident 
  when 
  the 
  resistance 
  is 
  

   reduced 
  to 
  1000 
  ohms. 
  

  

  