The Song of the Open Wire

Today I am showcasing a fantastic website:

 The Song of the Open Wire

This website covers the history of wired telecommunications from 1843-2020.
Filled with articles and photos covering telegraphy, telephones, physical systems, personnel, memoirs, and has technical articles, historic photos and more.

This is a site well worth the perusal if you are interested in how these systems were built, maintained, and operated.

Below in its entirety is an article, the first in a series, on the analysis of telegraph lines, just to give you a taste for what this site contains!

Enjoy
73
Ciao
KJ

DC Transmission Line Modelling: Initial Studies on Telegraph Lines

By Tom Hagen

Introduction

This set of articles is intended to be an introduction to transmission lines and transmission line parameters.  I’m hoping that anyone interested in this topic will get a good intuitive feel on why open parallel wire communication systems are built the way they are.  This subject can be very technical if you go into the mathematical constructs.  It took a number of “first rank” physicists several decades in the 19th Century to get to the point of where the behavior of parallel open wire systems could be definitely modeled, characterized, engineered, and reliably operated in the real world.

I’ll add to this section of Doug’s website as time permits, so check back every few months and I hope to add one or two more articles after the first one.

Sections:

DC Transmission Line Modelling:

• Theory of capacitance and resistance
• Underground vs. overhead telegraph lines (early work)
• Undersea telegraph cables
• William Thomson’s (Lord Kelvin) efforts
• Thomson’s square law

Traveling Wave Transmission Line Modelling:

The work of the “Maxwellians”

• Comparison of DC and AC transmission line characteristics
• Distributed parameters of the transmission line
• Characteristic Impedance of the transmission line
• Travelling waves on transmission line
• Group delay problems on transmission line

Practical Examples:

• Distributed inductance to improve telegraph cable speed
• Loading coils on telephone lines

Open Wire Telephone Lines: Application of transmission line characteristics to open wire lines and technology.

Some Basics

The first inklings that long wires behave differently than short ones came about during he early development of the first telegraph systems in the early to middle Nineteenth Century.  It was observed that a wire acts one way when it is mounted overhead on poles and insulators and another when it was laid underground.  Experiments performed in the 1820s showed that a wire laid underground or in water passes electrical signals more slowly than a wire held overhead in air.  Michael Faraday (1791-1867), explained this effect as an effect of the electrical capacitance between the wire and the medium surrounding it.  Electrical capacitors were known to scientists by this time because the first electrical charge storage device, the Leyden Jar, was invented in the middle Eighteenth Century.

Referring to the below figures, an electrical capacitor is formed between the ire and the medium.  An electrical capacitor stores energy in the form of an electrical field between two conductors in close proximity.

A long wire buried in the ground can take on an electrical charge if you connect a voltage source such as a battery to it and a ground rod driven into the ground.  This is similar to giving a balloon a charge of static electricity when you rub it against a cloth.

Under the right conditions, i.e., if the wire is long enough and if the charge leakage to the earth is low enough, you can measure the retained charge that results in a measurable voltage between the wire and the Earth.

Fraser’s Calendar and Telegraphy Notebook 1872

 This is a real gem of a find from the Internet Archive courtesy of Alberta MTC member Marian Gibbard.

Fraser’s Calendar and Telegraphy Notebook from 1872 is fascinating look at the telegraph in British India in the latter half of the 19th C.

You can check out the Internet Archive copy here:
https://archive.org/details/dli.ministry.02181/mode/2up

The book is a calendar/log book for those working for the Indian Telegraph which was under the control of the Colonial Government much as the Postal Telegraph was in Britain. However, what makes this book particularly interesting is the wealth of information on the state of telegraphy at that time, theory, practice, and practical information on running a telegraph line across such a diverse country as India.

 At 101 pages, a third of which is the log book with a page for each month of 1872 and 1873, there is an amazing amount of information here, weights and measures, calculating distances for mapping, strengths of wire, problems with escapes caused by damp spider webs, electrical theory, regulations, rates, legislation from the government etc.

There is also very practical and useful information ranging from how to load a cap and ball pistol in damp conditions to how to treat "strangles", a dangerous disease of horses Marian tells me.

Also of interest is the Morse Code being referenced. It is the Continental Code not our American/Railway code which, given that this was published in 1872 makes it one of the earlier references to that code that I have seen! Of course by 1872 the globe was crisscrossed with undersea cables most of which used that code .

Worth a perusal.

73
Ciao
Kevin Jepson
Editor

Modern Practice of the Electric Telegraph 1892

 Today your humble editor received a real treasure!

A paper copy of Pope's "Modern Practice of the Electric Telegraph" written in 1892.
This magnificent book is produced in paperback form by the Leopold Classic Library from a scanned copy, made by Google I believe.
I have a PDF of the scanned copy of the 1874 edition from the Internet Archive but nothing compares (at least to me) to being able to peruse such old documents in paper form.

 Inside this book is a fascinating look at the state of electricity and electrical apparatus at the end of the 19th Century. There is practical advise on the design, construction, and use of the telegraph. Also trouble shooting tips for when things don't work!

There are 185 illustrations in this book that help to show not only the principles that Pope is describing, but are also a pleasant snapshot of the state of the technology at the time. 

I have perused the PDF file quite a bit but I have to say that being able to flip back and forth and wander around the book in it's physical form really helps me to cement my understanding and gives me a great appreciation for the technicians and craftsmen who created these globe spanning systems even when their understanding of the fundamental science was primitive in the extreme.

 

There were several editions of this book. The Internet archive has at least three that I have found one from 1866, 1874 and one from 1899.

All the PDF copies are in good shape with the scanned illustrations being very clear.

The paper copy I have was produced from the best scanned copy that was available and has the same detailed and clear illustrations.

Of interest to those of us struggling to lear the code and improve our sending and copying is a short section at the very end of the book with "Hints for Learners". Definitely worth a gander.

I found this page, the last page of the text, to be particularly apropos to me and the Heritage Park's gang of happy amateurs.
I have included a photo of the page.

Enjoy
73