hi there everyone

I'm currently reading a book called "Code" by Charles Petzold which is
essentially a history and overview of computer technology, quite
entertainingly told. I've just read the section on telegraphs and
relays and am confused by something he has written.

He explains the basic principle of the telegraph, and goes on to show
with some simple Ohm's Law calculations that you can't extend the
length of telegraph wires indefinitely due to the loop resistance
etc., hence the need for the invention of the relay.

However, I am a bit puzzled by his summing-up quote for this chapter:
"Regardless of the thickness of the wires and the high levels of
voltage, telegraph wires simply couldn't be continued indefinitely".
Now I would have thought the restriction was *exactly* due to the
limitations on wire thickness and voltage (ie the practical problems
with manufacturing telegraph cables and voltaic cells at that time).
Or am I doing Mr.Petzold an injustice, when perhaps there was some
other limiting factor ?
I have read somewhere that there were problems with insulation for
very long cables, is this perhaps something to do with it ?

Any thoughts you may have are welcomed,

best rgds

griffph