The machine sits under the typewriter like a deck, and obviously the keys are somehow connected to it.   The photos are
reasonably good, but it is impossible to figure much out.
  "He takes two ordinary typewriters of standard make, such as the
  Stearns, L.C. Smith, Underwood or Monarch. The two that the writer observed
  were the "Stearns," and they were the same machines that one would
  buy in the market for office use. Each was equipped with the electrical
  apparatus to set the electrical waves n motion and record them at the other
  end.
  The operator sits at the sending typewriter and operates the machine just
  as the ordinary stenographer types letters. The message is recorded on the
  receiving instrument as perfectly as though it were a carbon copy of the
  original. Likewise the sending machine makes a copy of the message just as it
  is sent. The system is a sending, receiving and recording operation, all in
  one.
  Each letter on the keyboard, as well as the characters, numerals and
  punctuation marks has its own individual combination of electrical impulses.
  By magnetic attraction the types bars on the receiving machine are attracted
  toward the roller where the paper rests.
  When the letter "A", for example, is struck on the key of the
  sending machine, a set of electrical impulses is set in motion over the wire
  which releases the letter "A" on the receiving machine and the type
  prints the letter on the paper roll. So on through the whole keyboard the
  operation is the same. In like manner, the shift key, the device for changing
  from capitals to small letters and vice versa, the spacing between words, the
  return of the carriage and the spacing for the next line, all are operated
  automatically in simultaneous action with the movements of the sending
  machine. This anyone familiar with the letters on the keyboard of any
  typewriter can send a message just as easily as he or she would typewrite a
  letter; and the message is recorded on the receiving machine in page form,
  corresponding to the usual typewritten business communication.