Re: [telecom] History trans-Atlantic cable

> The Bell System opened a voice cable across the Atlantic > in the mid 1950s. This was a major improvement since > the radio was unreliable and inadequate.

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 -

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"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 Moderator

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Julian Thomas
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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."

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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:

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Here is an article about a cable between Florida and Cuba

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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

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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?"


Reply to
Bill Horne

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.

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