[GreenKeys] Ticker-tape first unveiled 1867

[Jim Haynes]

The baseball ticker as I remember it - the wheel was rotated by a ratchet
mechanism driven by approx. 20 Hz polarity reversals on the line.  When
the desired character to print was over the hammer the reversals would
pause and the print hammer would hit the tape against the wheel.

There was a worm wheel with a projecting peg.  After several rotations
of the wheel the peg would engage an arm and stop further rotation of
the wheel even though the reversals continued.  This took care of the
resynchronization problem.  Every print operation popped the follower
arm away from the worm wheel and a spring took it back to the starting
position.  So as long as printing was taking place the type wheel kept
rotating, never getting stopped by the stop arm.

All this is described in an article in Encyclopedia Americana in the
late 1950s.  It's good to buy (cheap) an old encyclopedia if you want
to understand how technology worked back then.