[GreenKeys] How were teletypes connected across long distances?

[Robert Nickels]

On 11/24/2023 11:00 AM, Sheldon Daitch via GreenKeys wrote:
> Lenkurt 25A single channel tone decoder

Interesting stuff!   It brought to mind the "black box" that was on the 
wall or near the AP teletype machines at radio stations (and other wire 
services).    It was all part of the service and no one gave much 
thought to how it actually worked.

I was curious and found a document called  "The Lenkurt Demodulator" 
that has a clear description of how "telegraph transmission over voice 
frequency multiplex system" worked.  It's a pdf file that can be 
downloaded here: https://tinyurl.com/yc4rfbwt

73, Bob W9RAN