An interesting story

[gar]

190617-2501 EDT

See https://en.wikipedia.org/wiki/Electrical_telegraph

Many interesting things have been invented since George Washington's time.

.

 

[gar]

190618-0825 EDT

When I made the first post my goal had been to find out what voltage was used in telegraph circuits. The link in that first post did not provide the answer, but the link was interesting so I created the post. It was late and I did not search further.

This morning I looked again and found this link
http://www.w1tp.com/pertel.htm
However, 6 V seems low to communicate over any substantial distance. No mention of ground rod resistance in the later systems that used the earth as one wire.

Modifying the search string a little more and I found this very good discussion
https://www.mikeholt.com/mojonewsar...-and-the-Modern-Telegraph-System~20050607.php
So here we see large voltages were used, thus many batteries in series, and a telegraph operator would not want to get their body across an open telegraph key.

.

 

[StarCat]

Another Interesting one

Another Interesting one

190618-0825 EDT

When I made the first post my goal had been to find out what voltage was used in telegraph circuits. The link in that first post did not provide the answer, but the link was interesting so I created the post. It was late and I did not search further.

This morning I looked again and found this link
http://www.w1tp.com/pertel.htm
However, 6 V seems low to communicate over any substantial distance. No mention of ground rod resistance in the later systems that used the earth as one wire.

Modifying the search string a little more and I found this very good discussion
https://www.mikeholt.com/mojonewsar...-and-the-Modern-Telegraph-System~20050607.php
So here we see large voltages were used, thus many batteries in series, and a telegraph operator would not want to get their body across an open telegraph key.

.

Another interesting one would be Raymond Royal Rifes original machine design. Unfortunately this will likely never be known, due to the Nefarious Forces that destroyed the man and the brilliance of his Life's Work.

Star

 

[electrofelon]

I was watching a documentary on the first trans Atlantic telegraph cables, and one of the first attempts they shorted it out by cranking the voltage up too high, but they did not provide specific voltage numbers.

The "TAT" series, with TAT-1 being the first telephone cable (woo hoo, 35 simultaneous telephone calls!) has has 14 cables I believe, the newer ones being fiber optic of course. I always wondered about the voltage of the earliest ones, and if anyone has thought about salvaging the decommissioned ones for scrap.

 

[growler]

So here we see large voltages were used, thus many batteries in series, and a telegraph operator would not want to get their body across an open telegraph key.

.

I was watching a documentary on the first trans Atlantic telegraph cables, and one of the first attempts they shorted it out by cranking the voltage up too high, but they did not provide specific voltage numbers.

What I find really interesting is that until they tried the trans-Atlantic telegraph cable with no options for relay stations no one had considered the need for an amplifier.

 

[drcampbell]

... a telegraph operator would not want to get their body across an open telegraph key.

Back in the days of vacuum tubes, it was common for radio receivers to use a non-finger-safe 2000-ohm headset directly in the plate circuit, which was supplied with 150-250 DC volts.

 

[Besoeker3]

190617-2501 EDT

See https://en.wikipedia.org/wiki/Electrical_telegraph

Many interesting things have been invented since George Washington's time.

Indeed.
Quite a few in Scotland, a country with a tiny population.
A light-hearted link.

https://www.theayelife.com/scottish-inventions/

 

[growler]

Indeed.
Quite a few in Scotland, a country with a tiny population.
A light-hearted link.

https://www.theayelife.com/scottish-inventions/

They didn't even mention "cross dressing".

 

[drcampbell]

... a telegraph operator would not want to get their body across an open telegraph key.

It would have been possible to connect the telegraph key to a low-voltage source and use a relay to isolate the operator from a high-voltage, long-distance line. Do you know if that was ever implemented?

 

[retirede]

It would have been possible to connect the telegraph key to a low-voltage source and use a relay to isolate the operator from a high-voltage, long-distance line. Do you know if that was ever implemented?

I wonder if relays in the day would have been too slow to keep up with a good telegraph operator?

 

[growler]

It would have been possible to connect the telegraph key to a low-voltage source and use a relay to isolate the operator from a high-voltage, long-distance line. Do you know if that was ever implemented?

I wonder if relays in the day would have been too slow to keep up with a good telegraph operator?

The first amplifiers were relays that allowed them to use a weak signal from across the Atlantic to operate a telegraph key. Can you imagine trying to send enough power to operate an electro-magnet.

 

[Besoeker3]

They didn't even mention "cross dressing".

Very droll............

 

[PaulMmn]

I was watching a documentary on the first trans Atlantic telegraph cables, and one of the first attempts they shorted it out by cranking the voltage up too high, but they did not provide specific voltage numbers.

The "TAT" series, with TAT-1 being the first telephone cable (woo hoo, 35 simultaneous telephone calls!) has has 14 cables I believe, the newer ones being fiber optic of course. I always wondered about the voltage of the earliest ones, and if anyone has thought about salvaging the decommissioned ones for scrap.

If the original voice circuits are still usable, they're probably still being used.

re: cable circuits from Florida to Cuba-- Reliable Rumours say that even though official contact was cut off, the weekly circuit test schedule was duly maintained at both ends, and the circuits were still up and running throughout the cold war.

 

[synchro]

The discussion of early telegraphy and transatlantic cables reminds me of all the contributions that Oliver Heaviside made to those areas and to so many others in electrical engineering and science.


https://www.fourmilab.ch/fourmilog/archives/2018-11/001795.html

 

[gar]

190618-1740 EDT

synchro:

Thanks for the reference. A very good read.

.

 

[electrofelon]

If the original voice circuits are still usable, they're probably still being used.

re: cable circuits from Florida to Cuba-- Reliable Rumours say that even though official contact was cut off, the weekly circuit test schedule was duly maintained at both ends, and the circuits were still up and running throughout the cold war.

TAT 1 thru 11 have all been taken out of service, with 12/13 taken out of "normal commercial service", according to wikipedia. Most of the older ones were in service for 22 year, and the newer ones appear to have only been in service for about 10 years before taken offline. Perhaps they become obsolete and not worth maintaining?

 

[synchro]

Back in the days of vacuum tubes, it was common for radio receivers to use a non-finger-safe 2000-ohm headset directly in the plate circuit, which was supplied with 150-250 DC volts.

And Popular Mechanics would publish articles how to build a shortwave radio on a wooden breadboard connected to a 110V line cord and headphones:

https://books.google.com/books?id=1...&q=popular mechanics 117n7 dx economy&f=false

 

[drcampbell]

... Can you imagine trying to send enough power to operate an electro-magnet.

Today, there are reed relays that actuate on 0.1W - 5V, 20 mA, which could then actuate a larger relay. My bigger concern would be line capacitance and operating speed.

... re: cable circuits from Florida to Cuba-- Reliable Rumours say ... the circuits were still up and running throughout the cold war.

Probably a good thing. Gives each side the opportunity to pick up the phone and convey important messages such as, "That wasn't a launch. It was a motor-vehicle crash at a missile-fuel depot.".

They didn't even mention cross dressing.

That'd be a Scottish woman wearing a kilt?