Re: [telecom] History trans-Atlantic cable

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I was working at Bell Labs back then; I remember some of what we heard from
the group.

- The Teredo worm is the enemy of submerged cable!

- They were trying to extrapolate the lifetime of tubes [hoping for 20
  yrs] on the basis of less than a year of data. This was JUST before
  transistors appeared, let alone became reliable.

Julian Thomas   -

"I wish to God these calculations had been executed by steam!"
-Charles Babbage

***** Moderator's Note *****

I thought the Teredo worm was the reason ships had to cover their
bottoms with copper. I'm surprised that the worms could range to the
depths of undersea cables.

Bill Horne

Re: [telecom] History trans-Atlantic cable
On Thursday, December 12, 2019 at 12:26:05 AM UTC-5, Julian Thomas wrote:
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Research into undersea cables had been going on for some time.  Bell
had experience with shorter cables.  There was extensive experience
with Western Union telegraph cables, although telegraph is less
demanding than voice.

For instance, here is an article on the impact of fishing on cables:

Here is an article about a cable between Florida and Cuba

The transistor was invented in 1948, although it took roughly ten
years for it be developed into a commercial viable product.  That is,
able to be manufactured at a cost less than a tube and reliable enough
to be useful.  Initial applications were portable radios, though tubes
were continued to be used in consumer audio devices for years.

When computers came along, computer makers found that tubes used in
audio devices were not reliable enough for high speed digital service.
Tiny faults that weren't noticed in audio service would cause computer
bit errors.  Computer makers developed premium grade tubes where the
internal materials were of a higher quality and yield better
performance, and also physical placement of the structures were more
precise.  Tubes were also made under cleaner conditions.

Here is an ad for RCA premium tubes


[public replies please]

Re: [telecom] History trans-Atlantic cable
On 12/10/19 8:20 PM, Julian Thomas wrote:
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Consider that the cable must come up from below at each end.

This from Wikipedia: "Many early cables suffered from attack by
sealife.  The insulation could be eaten, for instance, by species of
Teredo (shipworm) and Xylophaga. Hemp laid between the steel wire
armouring gave pests a route to eat their way in. Damaged armouring,
which was not uncommon, also provided an entrance. Cases of sharks
biting cables and attacks by sawfish have been recorded."

Re: [telecom] History trans-Atlantic cable
On Thu, Dec 12, 2019 at 12:40:15PM -0800, Dave Platt wrote:
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OMG, I'm 15-years-old-again! Can we talk about the mu of a 12AX7?

No, wait, let's involve everyone: who can name the "All American Five?"


Bill Horne
(Remove QRM from my email address to write to me directly)

Re: [telecom] History trans-Atlantic cable
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TAT-1 had 51 voice channels.  By 1978, TAT-6 was in service with 4000
channels, later expanded to 10,000, and TAT-7 was being laid with
another 4000 channels expandable to 10,000.  If anything, it's
surprising that they kept TAT-1 in use as long as they did since it
was so tiny and obsolete.

I'm confident that the repeaters worked up to spec.  Western
Electric's designs were very, very, conservative.

TAT-1 was retrieved and repaired at least once due to damage from a
fishing trawler.  Here's a report of a repair in 1959 which took
slightly over three days from damage to full repair.  The damage was
in shallow water close to the Scotland end of the cable and a suitable
cable ship was in port nearby.

John Levine,, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail.

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