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A couple weeks ago my local PBS station broadcast a show about the very first transatlantic telegraph line. Mostly it was about the financing and cable laying voyages and very little about the things a geek like me was interested in: the electrical characteristics of the cable and how fast they were able to transmit messages. Only by reviewing the transcript of the show, reading a Wikipedia article and other articles was I able to get the facts I wanted (and more). Here, then are some of the facts I acquired: - The first successful transatlantic cable was laid in 1858. - It stretched from Newfoundland to the coast of Ireland. - A separate cable from New York to Newfoundland was already laid a couple years prior to the 1858 cable. - The electricity was too weak at the far end of the cable and so Lord Kelvin invented the mirror galvanometer which could detect very slight voltage differences. - Reception was very poor despite the fact that hundreds of volts of electricity was applied at the source end of the cable. - It took two minutes to send the first character (or letter) across the cable. That is equal to 0.1 words a minute (and you thought your modem was slow ). - The first message on the cable, a message from Queen Victoria to U.S. President Buchanan, took over 17 hours to transmit. - At the source end of the cable over 500 volts were applied. In an attempt to improve performance, the voltage was increased until it reached 2,000 volts and the cable failed (this high voltage most likely broke down the insulation). - The 1858 cable only operated for 23 days. So that was it for the 1858 cable. When word spread that the cable failed, there was a tremendous reaction by the press and public. People hinted that the whole thing was a hoax (conspiracy theories in the 1850's, go figure). As a result, a committee of inquiry was formed to investigate the failure. The committee found a number of problems with the 1858 cable. Mostly it had to do with how the cable was designed and built. In fact, Cyrus West Field, the guy who spearheaded the 1858 cable, knew about the flaws but went ahead anyway. The committe also discovered that a lot of the problems with the cable had to do with a poor understanding of electricity. In fact, Wildman Whitehouse, the chief electrician on the 1858 cable, had a lot of hokey ideas about science and electricity and really didn't know what he was doing (he was an English surgeon before becoming involved in the 1858 cable - hardly the qualifications necessary to head such a project). A significant result from the inquiry was the recommendation for the definition of standardized units. Thus, the definition of Volts, Ohms, Ampheres and Watts were a direct result of this committee of inquiry. The most important contribution of the committee was the fact that it existed at all. It set a precedent for other inquiries into engineering failures that were yet to come including the sinking of the Titanic and the Challenger explosion. Nowadays, such inquiries are routine following disasters in an attempt to prevent such mistakes from repeating. It wasn't until 1866 before another transatlantic cable was attempted. The civil war, the inquiry and Cyrus Field's difficulty in garnering more finances were the main reasons for the delay. Some facts about the 1866 cable: - Cable manufacturing techniques and message sending methods improved considerably since 1858. - It could transmit up to 8 words a minute which is 50 times faster than the 1858 cable (still a LOT slower tha a 300 baud modem, which is about 360 words per minute). - The 1866 cable carried 1,000 messages per month, at up to ten dollars a word. - Once the 1866 cable became operational, Europe and America have been continously connected elecronically ever since (new cables became operational before the 1866 cable failed). - The 1866 cable, along with cables to the rest of Europe and Africa made London the communications center of the world. No less than 11 cables radiated from the city to connect it to the world. The lack of a repeater station is the main reason for the slow transmission speeds (kinda hard to put a working repeater under the ocean). It wasn't until the 20th century that transmission speeds could reach 120 words per minute. Many modern cables route through Iceland so that repeaters can amplify the incoming signals and improve performance. The first transatlantic telephone line wasn't attempted until 1956. It's a lot more difficult to transmit a voice signal across a transatlantic cable than a telegraph signal. The first transatlantic cable, labeled TAT-1 carried 36 channels - that's 36 simultaneous telephone calls. Each channel had a bandwidth of 4 KHz which could carry a human voce (but the sound was really tinny). Today, transatlantic cables are capable of transmitting in the Gigabit per second range, use fiberoptic technology and self healing ring topology. So, if you ever read an E-mail from a friend overseas or visit an overseas web site, keep these facts in mind.
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