
Hydraulic Telegraph - tikwidd
https://en.wikipedia.org/wiki/Hydraulic_telegraph
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nkrisc
Maybe I'm missing something, but with the Greek system why did they need to
use draining water as a time-keeping method? Why not, after some
acknowledgement sequence, does the signaler not simply wave the touch a
specific number of times which the receiver could use to correlate with a
predetermined list of possible messages?

For example, signaler holds touch aloft continuously. Receiver notices and
does the same to acknowledge. Signaler now waves the touch seven times.
Receiver checks chart for which message 7 waves correlates to. Is that not
effectively the same as the described method in the article but with less room
for error due to timing?

You also wouldn't need to keep the devices themselves calibrated, as if one
drained faster than the other, you'll have a problem. You only need a mutually
agreed upon chart of messages which is already a requirement with the water
method.

Basically, semaphore. Why not just semaphore? What is the advantage to their
method? Is the timing method maybe easier if you were dealing with, say, 50
messages on the vessel? As opposed to coming up with a way to encode 50
different messages?

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rtkwe
Light on or off is a clear signal over a much longer distance than a light
moving only a few feet. A simple candle can be seen a very long distance on a
dark night but just moving it back and forth gets lost. There were no means of
visual magnification available which is what makes semaphore possible over
usable distances.

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ncmncm
So, instead of waving the torch in the open you wave it next to a wall so it
appears to go on and off. Same question.

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nkrisc
I thought the same as well. Clearly the ancient Greeks weren't morons so
there's probably a reason they did it the way they did. Thinking about it
more, their system is probably much easier for a novice to use, or some random
soldier grabbed for signal duty. There's no need to count and keep track of
torch waves. The synchronization protocol seems pretty simple and the process
afterwards is equally simple.

Hell, your soldier doesn't even need to know how to count, if that was even a
problem for the Greeks.

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mannykannot
In the Roman version, the hydraulic part is a clock for generating and
measuring signals having a specific duration.

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rtkwe
Yes. In a time before we really knew how to accurately measure short periods
of time flowing water was one of the few ways humans had to meter out time.

In theory a pendulum with the same weight and length could have served the
same purpose with some limitations on the number of messages it could
potentially convey.

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yummypaint
Reminds me of the paris pneumatic clock system that would be built 40 years
after the british telegraph.
[https://news.ycombinator.com/item?id=19441300](https://news.ycombinator.com/item?id=19441300)

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est31
pneumatics are still used in organs today! (Not new ones, but old still
deployed ones still have them)

[https://upload.wikimedia.org/wikipedia/commons/5/51/Salemer_...](https://upload.wikimedia.org/wikipedia/commons/5/51/Salemer_M%C3%BCnster_Orgel_innen_Pneumatische_Traktur.jpg)

[https://en.wikipedia.org/wiki/Tubular-
pneumatic_action](https://en.wikipedia.org/wiki/Tubular-pneumatic_action)

~~~
dwringer
This made me recall reading about Douglas Engelbart's project from SRI (whence
the computer mouse originated) that used a 5-key chording keyset that had
pneumatic actuators for using the keys to output a data stream to the user
haptically (from my reading it was unclear if this functionality was ever
intended to be put in the mouse as well, which was used in the opposing hand).
I wonder if anyone is aware of any existing modern (DIY?) projects to bring
such a thing back to life?

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JoeAltmaier
Could have used the aqueduct as a telegraph as early as 7th century BCE - put
a written message in the equivalent of a rubber duck, drop it in. A spotter on
the other end dips it out and delivers the message. How could no one have
thought of that?

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krilly
I was just about to ask HN to come up with some communication devices using
only ancient technology.

Although your rubber duck system would require less manpower than a system of
signal fires, it would be MUCH slower, and probably even slower than the
chains of horse riders that delivered messages Pony Express-style across the
Roman Empire. In an emergency, a message could be transferred over 100 miles a
day.

[https://en.wikipedia.org/wiki/Cursus_publicus](https://en.wikipedia.org/wiki/Cursus_publicus)

~~~
JoeAltmaier
Oh! And for your ancient-networking subject, I submit:

    
    
      * grow trees in rows; cut them in ascii sequences (a stump is a 0). Visible for miles!
      * scratch dated messages in turtles' shells; sample shells continuously and collate
      * spread gossip where the subject is a code e.g. marital infidelity means one thing, sexual preference another. Collect gossip and reconstruct. Use political topics for ack and nack. 
      * Grow crops each year to encode the message: corn is a 1, soybeans a 0. Study crop market reports. Caution: baud rate is low and noise level high, recommend using ECC
      * Become a fashion icon. Adjust skirt lengths microscopically and seasonally to encode multiple bits! A plus: observation and measurement has side benefits
    

Let me know if any of these suit your purposes. I release them to the public
domain.

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rtkwe
Friendly reminder that the code block style is basically unreadable on mobile
(and not so great on desktop either) because it doesn't wordwrap.

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JoeAltmaier
Dunno how to do lists

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rtkwe
* Just put an asterix or something

* Don't indent by more than one space

* Hackernews doesn't support proper list formats or really anything beyond _italics_ , urls, and codeblocks.

