They actually had a system back then to get an
approximation of how far out the break was but I bet it wasn't
very accurate. They would try to read the resistance of the wire
since the broken end of the cable would be exposed to the sea. It
was still pretty hit and miss. In the first place, it would only
tell you about the first break. There could be 100 more breaks
after that one, but the first break is where it stops as far as
electricity is concerned.
There really was not a high-quality Transatlantic cable
until the middle of the 20TH century. In the fifties, cable was
laid that actually had amplifiers every so many miles. These
were called repeaters and they contained vacuum tubes. The
tubes normally had 6-volt filaments but they were run at 3
volts since they would last almost forever at the lower voltage
down there in the cold dark ocean.
What they did was to transmit a spectrum of numerous
radio frequencies with each frequency supporting upper and lower
sideband voice channels or one or two frequency-shift-keying
data channels which, back in the late fifties, would have been
mostly Teletype services of various kinds for news wires,
business and government agencies.
The tubes or valves would not have had quite as much
amplifier gain running at the lower filament voltage, but they
would have had enough for the job at hand so they reportedly
gave long and relatively trouble-free service.
I understand that when there was a cable break, the ship
sent to fix it would drop a weighted probe in to the water which
contained a sort of antenna, probably a magnetic pickup of some
kind.
They would then sweep back and forth and listen for
carriers on the frequencies used in the cable and when they
heard the signals, they had to be close since sea water does not
propagate radio signals well.
This was, however, light years ahead of what they had to
do before the modern days which, in many respects, started
around the time of World War II.
If you wonder how communications were handled between
Europe and North America before any modern transatlantic cables,
it was mostly done by short wave radio.
Martin
Travis Siegel writes:
> I read an article somewhere (can't remember where, maybe science news)
> describing the process of patching the transatlantic cable. They used a
> ship (a rather large one) and it had hooks that dropped down to the bottom
> of the ocean, grabbed both ends of the broken cable, and brought it up to
> the surface. They patched it (don't remember how) then dropped it again.
> It
> fixed the cable, though the article didn't say for how long. It's
> interesting though, how much technology has progressed since then. These
> days, they can tell you not only that the cable is broken, but where it is
> broken, and that I find interesting. Anyone know how that's done?
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