None  of  these  arrangements,  however,  seems  to  possess  the
advantages  which  are  secured  when  the  annunciators  are  placed
across  the  boards  below  the  spring-jacks,  with  the  operator's  key-


THE  MULTIPLE  SWITCHBOARD


231


board  below  the  annunciators,  and  the  shelf  for  holding  the  cords
and  pulleys  above  the  spring-jacks.
One  important  advantage  of  this  general  arrangement  is  that  it
allows  the  placing  of  the  boards  together,  end  to  end,  thus  enabling
an  operator  at  any  board  to  make  connections  between  the  spring-
jacks  upon  her  own  board  and  those  upon  the  adjacent  board,  in
cases  where  those  spring-jacks  are  nearer  than  the  correspond-
ing ones  upon  her  own  board.  .  ..
The  accompanying  cut  [fig.  91]  shows  the  jack  as  used  on  the  mul-
tiple board.  The  frame
of  the  jack  is  inserted  at
the  back  of  the  board  and
screwed  fast  by  a  lug
which  forms  a  portion  of
the  frame.
The  phosphor-bronze
spring,  and  the  contact
point  upon  which  it  FlG-  91-— Multiple  Jack  (1883).
normally  rests,  are  insu-
lated from  the  frame  of  the  jack  by  hard  rubber  bushings  and
plates.
The  connections  of  the  jacks  are  all  made  at  the  back  of  the
board,  and,  to  facilitate  this  work,  phosphor  bronze  connecting
pieces  are  extended  from  both  the  insulated  contact  point  and
spring,  bringing  all  the  connecting  points  together  in  one  plane
surface.
When  a  plug  is  inserted  into  the  jack  [fig.  92]  the  phosphor-bronze


FIG.  92. — Multiple  Jack  and  Plug  (1883).
spring  is  lifted  from  the  insulated  contact  point,  breaking  a  con-
nection therefrom,  and  a  new  connection  is  established  to  the  tip
of  the  inserted  plug  upon  which  the  new  spring  now  rests,  and
thence  to  the  cord  connecting  with  the  plug.
