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  134 
  j 
  

  

  Note 
  by 
  Mr. 
  van 
  der 
  Pol, 
  junr. 
  

   The 
  well-known 
  facts 
  respecting 
  the 
  division 
  of 
  current 
  

   between 
  a 
  telephone 
  and 
  its 
  shunt 
  circuit 
  are 
  correctly 
  stated 
  

   by 
  Prof. 
  Howe, 
  but 
  he 
  has 
  rather 
  lost 
  sight 
  of 
  the 
  motive 
  of 
  

   my 
  paper 
  and 
  of 
  certain 
  experimental 
  difficulties. 
  The 
  

   principal 
  object 
  in 
  view 
  was 
  to 
  test 
  whether 
  the 
  audibility 
  

   factor 
  could 
  be 
  considered 
  to 
  vary 
  as 
  suggested 
  by 
  Prof. 
  

   Love 
  with 
  the 
  received 
  antenna-current. 
  

  

  In 
  discussing 
  some 
  experiments 
  by 
  Dr. 
  Austin, 
  Prof. 
  Love 
  

   makes 
  use 
  of 
  the 
  audibility 
  factor 
  defined 
  as 
  R+S/S, 
  where 
  

   S 
  is 
  the 
  resistance 
  of 
  the 
  shunt 
  and 
  R 
  the 
  telephone 
  resistance*. 
  

   In 
  order 
  to 
  test 
  experimentally 
  his 
  suggestions 
  as 
  to 
  the 
  

   proportionality 
  of 
  the 
  so-defined 
  audibility 
  factor 
  to 
  the 
  first 
  

   power 
  or 
  square 
  of 
  the 
  antenna-current 
  I 
  had 
  to 
  use 
  the 
  

   same 
  constants. 
  My 
  experimental 
  results 
  appeared 
  to 
  be 
  in 
  

   close 
  agreement 
  with 
  Prof. 
  Love's 
  suggestions. 
  

  

  The 
  same 
  definition 
  (with 
  the 
  aid 
  of 
  the 
  telephone 
  resist- 
  

   ance) 
  of 
  the 
  audibility 
  factor 
  is 
  used 
  by 
  several 
  other 
  writers. 
  

   Prof. 
  Howe 
  refers 
  in 
  his 
  paper 
  to 
  a 
  yery 
  recent 
  publication 
  

   by 
  Austin 
  which 
  was 
  published 
  after 
  my 
  paper 
  had 
  been 
  

   sent 
  to 
  the 
  Philosophical 
  Magazine. 
  Here 
  Austin 
  refers 
  

   to 
  the 
  telephone-impedance, 
  but 
  on 
  the 
  other 
  hand, 
  in 
  a 
  

   former 
  paper 
  by 
  the 
  same 
  experimentalist, 
  he 
  defines 
  the 
  

   audibility 
  factor 
  using 
  the 
  telephone 
  resistance 
  instead 
  of 
  the 
  

   impedance 
  f 
  . 
  

  

  It 
  is 
  by 
  no 
  means 
  clear 
  whether 
  Austin 
  or 
  Hogan 
  em- 
  

   ployed 
  the 
  true 
  impedance 
  of 
  their 
  telephones 
  in 
  the 
  

   audibility 
  factor, 
  as 
  in 
  their 
  papers 
  cited 
  no 
  references 
  at 
  

   all 
  are 
  given 
  how 
  they 
  determined 
  these 
  impedances. 
  

  

  Further, 
  it 
  is 
  a 
  matter 
  of 
  considerable 
  difficulty 
  to 
  measure 
  

   the 
  true 
  impedance 
  of 
  a 
  telephone 
  when 
  used 
  as 
  in 
  Wireless 
  

   Telegraphy 
  in 
  series 
  with 
  a 
  crystal 
  detector, 
  and 
  therefore 
  

   traversed 
  by 
  an 
  intermittent 
  or 
  pulsatory 
  current, 
  the 
  wave- 
  

   form 
  of 
  which 
  is 
  not 
  known. 
  From 
  the 
  pronounced 
  variation 
  

   in 
  character 
  of 
  the 
  tone 
  in 
  the 
  telephone- 
  receiver 
  with 
  dif- 
  

   ferent 
  couplings 
  it 
  may 
  further 
  be 
  concluded 
  that, 
  probably 
  

   as 
  a 
  consequence 
  of 
  the 
  irregular 
  shape 
  of 
  the 
  characteristic 
  

   of 
  most 
  crystal 
  detectors, 
  the 
  telephone 
  current, 
  while 
  varying 
  

   in 
  intensity 
  also 
  (opposite 
  to 
  the 
  suggestion 
  of 
  Prof. 
  Howe) 
  

   varies 
  in 
  wave-form, 
  so 
  that 
  it 
  is 
  doubtful 
  if 
  the 
  ordinary 
  

   well-known 
  theory 
  of 
  sine-form 
  currents 
  may 
  be 
  applied 
  to 
  

   the 
  shunted 
  telephone 
  method. 
  

  

  Moreover, 
  the 
  current 
  in 
  the 
  telephone 
  circuit 
  at 
  the 
  

  

  * 
  Phil. 
  Trans. 
  Roy. 
  Soc. 
  Loud. 
  ccxv. 
  A. 
  p. 
  128 
  (1915). 
  

  

  t 
  Bull. 
  Bureau 
  of 
  Standards, 
  vi. 
  no. 
  4, 
  p. 
  531 
  (1910). 
  See 
  also 
  

   J. 
  Erskine 
  Murray, 
  'A 
  Handbook 
  of 
  Wireless 
  Telegraphy' 
  (1914), 
  

   p. 
  349. 
  

  

  