18 Mar
2008
18 Mar
'08
10:31 p.m.
Does anybody know what the signalling technique
(protocol) for these devices
was? I've always been curious about this but never had a mechanism to peruse.
My recollection from readings is that async bit-serial devices (tty, baudot
codes & c.) ("automated telegraphy") were not really successful until into
the 20th century, while these stock ticker networks were functioning decades
before that.
Looking at the photo gallery on the site and the apparent simplicity of the
mechanism, I'm guessing it was just a series of pulses to increment/rotate the
print wheel to select the character, followed by a pulse for a print hammer and
to advance the tape. There would then be the question of whether it was
I beleive that is correct. I have some information in old books on
telegraphy, I think there's a chapter on these fine machines in 'American
Telegraphy and the Encyclopaedia of the Telegraph' (which was reprinted
fairly recently). I will take a look.
separate circuits for the increment and print
solenoids or whether there was some
mechanism perhaps to separate an increment command from a print command sent over
one circuit (such as shorter vs longer pulses).
I think some were polarity-sensitive. A +ve pulse (say) stepped the print
wheel, a -ve pusle fired the hammer and moved the tape.
-tony