[GreenKeys] Dow Jones Broad Sheet News Printer

[Jim Haynes]

On Wed, 3 Apr 2013, John Nagle wrote:

>    The input to a "ticker" is two signals - one advances the
> typewheel one notch, and the other prints at the current typewheel
> position.  This, of course, creates a sync problem.  Edison's
> first major invention was a solution to that problem.  Sync
> usually involves some kind of resync on long pause or long
> pulse.  There are many approaches to this problem; there's
> a whole patent category called "unison devices" for this.
>
>    As with a clock, the escapement does not power the
> the mechanism.  The escapement holds back the mechanism.
> Here, the mechanism is driven by a motor through a slip clutch.

In some other ticker designs the escapement does power the typewheel
rotation mechanism.  I suppose that requires a lot more power delivered
over the line compared to one where the escapement does not power the
typewheel.
>
>    Ticker line inputs are usually polar - the line reverses
> DC polarity, rather than turning on and off.  Expect the
> escapement coils to work that way too; they probably require
> a reversing DC signal.
>
>    The bottom solenoid probably somehow triggers the long hammer
> behind the paper, which drives the paper against the typewheel
> for a print cycle.
>

In some ticker designs there are two circuits from the telegraph office
to the tickers: a polar one for the escapement and a single-current one
for the print hammer.  This was acceptable because a lot of tickers in a
city can be run off the same set of wires and within a city the wires are
not very long.

For long-distance transmission, where the cost of two sets of wires is
considerable, there is a scheme where a polar relay repeats the reversals,
while a more sluggish neutral relay operates when there is a pause in the
reversals, and controls the print magnet circuit.