Talk:Synchronization in telecommunications

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The Anome: the original contributor to this topic, Ian Wright, is one of the foremost experts in the world on network synchronisation! In particular, he sat on the committee which came up with the original MTIE algorithms.

History[edit]

Historically, synchronization in communications was a very hard problem. The first attempt at a teleprinter, by Bain, was a flop because he couldn't keep both ends in sync. Edison's big success with the stock ticker was because he came up with a clunky but effective "unison mechanism" to resync periodically. In the teleprinter world, Howard Krum finally came up with a good decoding mechanism for async signals around 1912, and that problem was solved.

Synchronization remained a problem well into the electronic era. The final solution to the synchronization problem came with the phase-locked loop. Once that became available, analog TVs, modems, tape drives, VCRs, and other common devices synchronized consistently. John Nagle (talk) 08:13, 3 January 2017 (UTC)[reply]

It would be nice to include this in the article. Can you suggest a citation? I'm not finding anything particularly usable in teleprinter. ~Kvng (talk) 23:15, 6 January 2017 (UTC)[reply]

Here's Edison's first stock ticker patent, with an explanation of the "unison mechanism".[1] That was Edison's first big commercial success. It's very simple; there's a "step" signal, which advances the print wheel with the alphabet, and a "print" signal. If the print wheel is stepped through two full revolutions without a "print" signal, it hits a stop at a known position. This resynchronizes the device if it is out of sync. It's a slow way to resync. Here's a brief reference from Rutgers.[2].

Here's a history of Teletype synchronization, and Krum's contribution, from Teletype Corporation in 1963.[3] Krum's big advance was that he came up with a reliable, mechanical way to do async serial to parallel conversion, the "teletype selector".

Analog television had to synchronize horizontal and vertical scanning. RCA's "Synchro-Lock" horizontal hold system (1946) was an early version of a phase-locked loop. This article has a historical overview: [4].

There's also history associated with early time-division multiplex systems for telegraphy, but I don't have a good cite for that. John Nagle (talk) 08:28, 7 January 2017 (UTC)[reply]