Insulators -- A Clinker ?

[nw-mailing-list at nwhs.org]

To all the savants and those blessed with knowledge and archives and all the 
like, I propose the following question...

How did the N&W mark the dispatcher's circuit in the pre-telephone days?  
Morse Telegraph circuits used only >>  ONE  <<  wire  (the earth was used for the 
"return" path, substituting for a wire.... Sorry buys, but that's just the 
way Samuel Morse invented the apparatus ! )

I seem to recall that telephones came into use on the N&W around 1912-1913.  
However, reliable long-distance (100 mile or so) telephone transmission  was 
possible only after the Lee DeForest developed the vacuum tube (1917, was 
it???) which enabled the building of the first "telephone repeaters."

So, how did the N&W mark the DS circuit in the pre-telephone days of 
single-wire Morse Telegraph circuits?

-- abram burnett
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