My take (right or wrong) is that teletype signals took over existing telegraph wires, hence the 120v loops, so you'd have to research that change likely in the 20s-30s, and evolved to Telex which adding switching. That evolved with TWX where they switched to standard telephone infra and abandoned the dedicated loops.

The problem is that transition may not have been well documented.

(Open to correction)


Jeff

On Apr 26, 2025, at 9:42 PM, Brenda Gentry via GreenKeys <[email protected]> wrote:



The mention of Navy RTTY  and water brought out a question-  when was the first transatlantic teletype cable system built?   What kind of keying did it use?

     B. Gentry,  KA2IVY

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Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
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______________________________________________________________
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Help: http://mailman.qth.net/mmfaq.htm
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Jordan Spencer Cunningham's GreenKeys Search Tool: https://teletype.net/gksearch
2002-to-present greenkeys archive: http://mailman.qth.net/pipermail/greenkeys/
1998-to-2001 greenkeys archive: http://mailman.qth.net/archive/greenkeys/greenkeys.html
Randy Guttery's 2001-to-2009 GreenKeys Search Tool: http://comcents.com/tty/greenkeyssearch.html

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