
The Paris Pneumatic Clock Network (2018) - Luc
http://www.douglas-self.com/MUSEUM/COMMS/airclock/airclock.htm
======
theoh
The Swiss railways have a slightly similar system of synchronization once per
minute, with an interesting nuance:

"The station clocks in Switzerland are synchronized by receiving an electrical
impulse from a central master clock at each full minute, advancing the minute
hand by one minute. The second hand is driven by an electrical motor
independent of the master clock. It requires only about 58.5 seconds to circle
the face, then the hand pauses briefly at the top of the clock. It starts a
new rotation as soon as it receives the next minute impulse from the master
clock.[4] This movement is emulated in some of the licensed timepieces made by
Mondaine."

(Wikipedia)

~~~
joezydeco
In the United States there were a number of private time services one could
subscribe to.

One of the largest was operated by Western Union. A telegraph line would be
used to send a synchronized signal a short period before the top of the hour,
which energized a solenoid in the clock. The minute hand would be pulled to
the :00 position and the clock would restart once the signal was released.
Commercial telegraph message traffic would be offline until this signal was
completed.

[https://www.hemmings.com/blog/article/tick-tock-whirrrrrr-
th...](https://www.hemmings.com/blog/article/tick-tock-whirrrrrr-thunk/)

There were also thousands of local "master clock" installations in schools and
other facilities. Lots of kids from the 70s and 80s probably remember the IBM
school clock:

[https://www.schoolhouse.com/products/1960s-ibm-standard-
issu...](https://www.schoolhouse.com/products/1960s-ibm-standard-issue-clock)

~~~
kingbirdy
I'd never considered the school clocks would be a centralized system, but it
makes sense. Interesting

~~~
theoh
NB the school clocks were only "locally" centralized...

~~~
yetihehe
Or even with "rolling updates",
[https://thedailywtf.com/articles/SyncingSunk](https://thedailywtf.com/articles/SyncingSunk)

------
tomatotomato37
The whole site for this is great. I really like the multitude of variations
they had in early steam/IC engines[0]; it reminds me a lot of the
expirementing we have in the software ecosystem today

[0a][http://www.douglas-
self.com/MUSEUM/POWER/unusualICeng/unusua...](http://www.douglas-
self.com/MUSEUM/POWER/unusualICeng/unusualICeng.htm)

[0b][http://www.douglas-
self.com/MUSEUM/POWER/unusualsteameng/unu...](http://www.douglas-
self.com/MUSEUM/POWER/unusualsteameng/unusualsteameng.htm)

~~~
MisterTea
I too think of these analogies buy my favorite subject is the early power
industry.

In the early days you had a multitude of frequencies and voltages. Higher
frequencies were desired for flicker free lighting but low frequency was
desirable as you could directly run commutated DC motors on low frequency AC
without brush arcing. This was important as AC was displacing DC in
distribution. Frequency selection was a compromise between motor
reuse/longevity and lighting flicker. In the end Westinghouse settled on 60Hz
and GE moved from 40Hz to 50Hz, then finally to 60Hz. German AEG which was a
licenser of Edison Electric/GE patents stuck with 50Hz and the rest is
history. The competition between AEG and Westinghouse is also why part of
Japan is 50Hz, the other, 60Hz. Little known fact: California was 50Hz until
1948 as GE was more popular on the west coast.

And to add to your original thought: If you watch Star Trek, everything is ran
by LCARS and everything seamlessly integrates. I wonder how and where the
industry will settle. Right now it feels like we're partly moving into a post
OS ecosystem where the applications have been abstracted from the underlying
system. I feel that it's a stop gap between something more akin to LCARS or
real life distributed systems like Erlang or Plan 9.

~~~
Scoundreller
Southern Ontario was still running on 25hz and only finished the transition in
the late 50s.

[http://www.execulink.com/~ocbogs/hist/oxhquiz/oxha046.html](http://www.execulink.com/~ocbogs/hist/oxhquiz/oxha046.html)

A steel mill still kept a hydroelectric station running in Niagara Falls at
25hz until 2009:

[http://www.technology.niagarac.on.ca/people/mcsele/interest/...](http://www.technology.niagarac.on.ca/people/mcsele/interest/rankine-
generating-station/)

~~~
lb1lf
Trains in Norway (and, presumably, also elsewhere) run on 16 2/3Hz AC.

This is a historical artifact - back in the day, electrical motors didn't fare
too well if fed with 50hz, so a lower frequency was desirable.

In airplanes, on the other hand, AC supply is typically 400Hz - as higher
frequency equates a smaller, lighter transformer for a given throughput.

~~~
usr1106
16 2/3 Hz or 16.7 Hz as the newer standardization says is used by all
countries that used AC early. 50 Hz wasn't feasible for railways before the
1960s or so.

16 2/3 Hz is at least in use in Germany, Switzerland, Austria, Sweden, and
Norway. In Germany development started already in the 1920s and regular usage
in the 1930s.

France, Finland, and Denmark for example were later with AC and they chose 50
Hz.

------
wazoox
It was almost certainly related to the "télégraphe pneumatique" messaging
system, that allowed to send mail and small objects extremely rapidly across
Paris in air-filled tubes:
[http://www.cix.co.uk/~mhayhurst/jdhayhurst/pneumatic/book1.h...](http://www.cix.co.uk/~mhayhurst/jdhayhurst/pneumatic/book1.html)

They had the compressed air generation available already! And this service was
available until 1984 (the last line was closed in 2004!).

More details on the French Wikipedia:
[https://fr.wikipedia.org/wiki/Tube_pneumatique](https://fr.wikipedia.org/wiki/Tube_pneumatique)

~~~
Aardwolf
> And this service was available until 1984 (the last line was closed in
> 2004!).

Odd that it fell out of favor, sending things around only became more popular
with all the internet shopping!

~~~
julienchastang
What's old can be new again! :-) My own great-grandmother was user of this
pneumatic mail network. Perhaps it was displaced by the Minitel -- another
remarkable invention that fell by the wayside.

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bambax
> _The pipes ran through the sewers of the city, and the tunnels of the Metro
> and the RER. (...) Operation began in 1880..._

The Paris Metro was inaugurated in 1900, and the RER in 1977, so this is
unlikely. (It would be possible to run pipes through tunnels before the
inauguration, but works on the Metro started no earlier than 1898).

[https://fr.wikipedia.org/wiki/Histoire_du_m%C3%A9tro_de_Pari...](https://fr.wikipedia.org/wiki/Histoire_du_m%C3%A9tro_de_Paris)

[https://fr.wikipedia.org/wiki/R%C3%A9seau_express_r%C3%A9gio...](https://fr.wikipedia.org/wiki/R%C3%A9seau_express_r%C3%A9gional_d%27%C3%8Ele-
de-France)

~~~
bunderbunder
According to TFA, the pneumatic clock system was in operation until 1927, so
there might have been plenty of time to make use of the Metro's tunnels at
least a little bit - perhaps to extend service to new buildings.

~~~
bambax
Maybe, but not at the time of implementation, and certainly never with the
RER.

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theamk
I liked the "explode all clocks" lever, which puts 73 PSI of pressure into the
lines designed for just 10 PSI.

> Note that there is a provision for connecting the high pressure air directly
> to the low-pressure reservoir, by means of valve f. Why you would want to do
> this I do not know, because as mentioned above I would have thought it would
> have caused all the clocks to explode.

~~~
nine_k
A military precaution? Any valuable system has to have a self-destruct button,
to prevent it from falling into enemy's hands.

------
userbinator
I wonder if any equipment from the system survives today... a quick Internet
search doesn't turn up anything but the old drawings and photos shown here.
Like a lot of other obsolete technology, it's one thing to read about it, but
I'd be very interested in seeing a (modern) photo.

------
zoobert
amazing. I had no idea it was so complex. Very informative. Thanks a lot

~~~
ams6110
I'm just sort of amazed that people felt it was worth that much apparent
expense and infrastructure to have synchronized public clocks. One central
clock tower with a bell would tell people what time it is.

~~~
theoh
Peter Galison's book "Einstein's Clocks, Poincaré's Maps" is based on his
personal speculation that it was the late 19th C preoccupation with
simultaneity that inspired the theory of relativity. Whether that's true or
not, he discusses the systems in the book.

"When I came back to the United States I started poking around old Swiss,
British, German, and American patents and industrial records, and it turns out
that there was an enormous industry in coordinated clocks in the late 19th
century. Suddenly the famous metaphor with which Einstein begins his 1905
paper began to look not so peculiar. Einstein asks us to interrogate what we
mean by simultaneity. He says, imagine a train comes into a station where you
are standing. If the hour hand of your watch just touches 7:00 as the train
pulls in front of your nose, then you would say that the train’s arrival and
your watch showing 7:00 were simultaneous. But what does it mean to say that
your clock ticks 7:00 at just the moment that a train arrives at a distant
station? Einstein goes on to develop a technique for saying what it would mean
to coordinate clocks, and explains that this is what simultaneity is. This
quasi-operational definition of simultaneity becomes the foundation of his
theory and leads to his startling conclusions that simultaneity depends on
frame of reference, that therefore length measurements are different in
different frames of reference, and to all of the other famous and amazing
results of relativity theory. Suddenly I could see that Einstein’s seemingly
abstract metaphor about trains and stations was actually both entirely
metaphorical and yet altogether literal. Far from being the only person
worried about the meaning of simultaneity—a lighthouse keeper in splendid
isolation--there was a vast industry of people worrying about what it meant to
say that a train was arriving at a distant train station. And they were
determining simultaneity by sending electrical signals down telegraph lines to
distant stations in ways very much like the way Einstein was describing in
that fateful paper."

------
dreamling
It's true the whole site is full of gems!

I wonder why Elon hasn't tried to go prop with high speed locos!
[http://www.douglas-
self.com/MUSEUM/LOCOLOCO/proprail/proprai...](http://www.douglas-
self.com/MUSEUM/LOCOLOCO/proprail/proprail.htm)

