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Mr. Burnett,</div>
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Thank you very much for your detailed explanation. I always enjoy your entries on the mailing list. And I appreciate your sharing of this information and the links to even more information. Since I am sending my signal through my radio antenna, I don't think
that I have the same concerns for arcing and burning contacts on the bug but it is always good to increase your knowledge base. I look forward to talking with you again in the future.</div>
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It won't be long before it's time to turn the earth for another season of quality turnips. One of my fondest childhood memories is sharing a freshly pulled turnip with my father as we worked in the family vegetable garden.</div>
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Take care,</div>
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Rick Huddle</div>
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Delaware, OH</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> NW-Mailing-List <nw-mailing-list-bounces@nwhs.org> on behalf of NW Mailing List via NW-Mailing-List <nw-mailing-list@nwhs.org><br>
<b>Sent:</b> Saturday, February 8, 2025 10:18 PM<br>
<b>To:</b> N&W Mailing List <nw-mailing-list@nwhs.org><br>
<b>Cc:</b> NW Mailing List <nw-mailing-list@nwhs.org><br>
<b>Subject:</b> Re: Telegraphers Paralysis</font>
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<div class="PlainText">Hon. Mr. Rick Huddle,<br>
Herder of Dots 'n Dashes,<br>
Delaware, Ohio<br>
<br>
Thanks for your inquiry ! and I am happy to see that you still use a Vibroplex. Anyone can do Quack-Quack on the radio, but it takes skill to do the Dots-and-Dashes thingie. I am glad you have developed that skill, and are enjoying it.<br>
<br>
1.) On each of the Vibrioplexes in the picture you asked about, there is a non-polarized condenser (I just can't get used to that new fangled word, capacitor !) wired in series with a resistor. They serve as "spark killers." Western Union set the standards.
As I recall, the caps were to be 0.25 microFarads, and the resistors to be 170 Ohms. The cap served to soak up the energy dissipated as a spark when the contacts opened, and the resistor served to limit the rate of capacitor's charging so that the cap was
not seen by the circuit as a short.<br>
<br>
If a telegraph wire is operating at, say, 140 volts, there is a lot of "pressure" (electromotive force) behind the moving (oscilating) stream of electrons. When the contacts on your telegraph key open, that moving stream of electrons wants to keep moving (oscilating)
and for a fraction of a second jumps across the gap between the contacts, producing a spark. The spark heats the contact metal and a little of the metal ionizes and vaporizes with each such spark. Over time, the contact metal is eroded, even though it is made
of a Tungsten-Silver alloy. "Spark killers" were wired across the contacts to soak up the spark and preserve the contact metal. (I met two of the very old men who had worked the El Paso - Mexico City circuit back in the 1920s. They told me a set of contacts
on their Vibroplexes lasted about two months. And Operators owned their own Vibroplexes, so da Comp'ny did not provide replacement parts ! )<br>
<br>
In the early days, the telegraph lines were energized by primary batteries (Copper + Zinc + acid in a glass jar, each such cell giving about 1.5 v DC, or a little less.) The Wire Chief seriesed as many cells as he needed, to develop sufficient voltage to push
out the required 60 miliamps of current (0.060 A, which is 1/16th of an Amp) needed to operate the instruments.<br>
<br>
So, how much voltage would be needed to operate a telegraph wire over a 100 mile railroad division? Well, let's add up the resistances. Copper wire has a resistance of somewhere around 10 Ohms per mile, so that's 10 X 100 = 1000 Ohms, just for the line wire.
Then figure perhaps 15 instruments, at 150 Ohms each = 2250 Ohms. Add 1000 Ohms for the wire + 2250 Ohms for the instruments = 3250 Ohms total circuit resistance. E=IxR. Solve for E. E = 0.060 X 3250 = 195 volts. And that assumes the wire is in perfect condition,
no broken insulators leaking current, no tree limbs touching the wire, etc. (There is no need to factor in the resistance of the return path, because telegraph circuits operate with just one wire and use the earth for a return path; and the earth is such an
efficient conductor that it adds no resistance to the overall circuit ! )<br>
<br>
This means our Wire Chief will have to line up about 100 primary battery cells to work this wire. 195 volts needed divided by 1.5 v. per cell = about 130 cells. For EACH wire ! Very cumbersome and very expensive to maintain.<br>
<br>
To avoid all these batteries, the "dynamo-machine" (steam operated, flywheel-driven DC electrical generator) was developed in the 1880s. Western Union had the commutators tapped to give DC current (instead of AC,) and standardized on 80 volts DC output for
each dynamo-machine. Seriesing two 80 volt machines together produced 160 volts output; seriesing three together gave 240 volts output. (Any current produced above the amount needed was burned off as heat, using banks of wire-wound resistors.)<br>
<br>
2.) In today's world, where all the old telegraph wires are gone and we work our 150 year old equipment over PC's connected to the Internet, the problem is a little different, and we protect the circuits with a different device. The problem we face today is
the energy in the magnetic flux which discharges every time a charged electro-magnetic telegraph coil is de-energized. When I restore instruments, I wind each coil with about 2300 turns of #32 gauge wire. My operating circuits are energized at 48v DC. An electrical
engineer friend used an osciloscope to check the "inductive kickback" from a pair of these telegraph coils, and saw nearly 700 volts for just a tiny fraction of a second. Wow ! What would a spike like that do to a transistor junction in your PC?<br>
<br>
That inductive kickback must be isolated from getting into the USB cord and frying something on the computer's motherboard. The device we use to do that is a transient surge suppressor, which consists of back-to-back Zenar Diodes in a single package. And we
put those not across the key contacts, but right across the coil binding posts on each sounder or relay. The Zenars will simply not allow the energy to pass out of the coils, and it is dissipated very quickly right at the coils. Given that we use transistor
switching, a problem is unlikely, but protecting with 35-cent semiconductor devices is cheap insurance against replacing motherboards !<br>
<br>
I understand just enough electronics to build my own interface equipment. But the computer theory and programming is far beyond my ken. It was developed by a software engineer from Boeing Corporation and he gives it all away here:<br>
<br>
<a href="https://sites.google.com/site/morsekob/home">https://sites.google.com/site/morsekob/home</a><br>
<br>
And yes, coupling 200 year old high voltage, high current inductive equipment to modern 5-volt high-speed semiconductors, probably drove him mad.<br>
<br>
I have put a few things up for you on Google Drive, and you (or anyone else) may download them here:<br>
<br>
<a href="https://drive.google.com/drive/folders/1pRHth4KVXJ6hEF-8YdeRGq1U3bPAJYbG?usp=sharing">https://drive.google.com/drive/folders/1pRHth4KVXJ6hEF-8YdeRGq1U3bPAJYbG?usp=sharing</a><br>
<br>
-- abram burnett<br>
Content Creator in the Turnip Space<br>
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