Talk:Frequency-division multiplexing

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Untitled[edit]

"The analog of frequency division multiplexing in the optical domain is known as wavelength division multiplexing."

Changed to: "The concept corresponding to frequency division multiplexing in the optical domain is known as wavelength division multiplexing."

This better reflects the intent of the writer... no need to confuse readers with the word "analog" in an article about frequency multiplexing. Indeed, the original word "analog" was linked to this article - http://en.wikipedia.org/wiki/Analog_signal - which has nothing to do with the word "analog" as it was used in context.

This is not an article![edit]

This is not an article, it's mostly just some pasted-in pictures of one specific implementation of a hierarchical FDM system, with absolutely no textual context given to explain the relevance of the three diagrams. Oli Filth 12:03, 1 September 2006 (UTC)[reply]

FDM is also Fused Deposition Modeling[edit]

Perhaps a disambiguation page with Fused Depsition Modeling (a type of rapid prototyping) or a listing in this stub would be helpful.

Not yet an article[edit]

I'm not an expert in CXR; rather an old Switchman but I know a few things. Added a few hints for the diagrams; that part still needs work. Also needs brief discussion of L and N CXR, pending writing articles about them. Converted the term "Single Sideband" into a link to the relevant theoretical article. Still got far to go. Jim.henderson 09:49, 3 October 2006 (UTC)[reply]

It's an article[edit]

It isn't a big or thorough article, but it's an antique topic and doesn't need that kind. It contains links to more modern theoretical topics. Over the past couple months I have organized it pretty well into non telephone and telephone sections, and explained the telephone diagrams. Rather than write everything I know about the long dead N and L-CXR, I'll remove the "call for expert" tag. Jim.henderson 17:42, 13 November 2006 (UTC)[reply]

IMO, the article shouldn't be about any particular/specific implementations of FDM, it should be about the theory of FDM itself; perhaps with some frequency plots, and an explanation of why one might want to use FDM (as opposed to, say, TDM).

All the stuff about the Bell implementation should not be in this article at all (apart from perhaps a brief mention along the lines of "phone systems used to use FDM..." in an "Applications" section, with some links to a separate article). The particular details about hierarchical multiplexing, implementation-specific frequencies, history, etc. completely obscure the central point, i.e. the hows and whys of FDM, which are barely covered. We certainly shouldn't be adding details about yet other phone systems!

The lack of basic "theory" was my rationale for originally adding the "call for expert" tag. Oli Filth 18:15, 13 November 2006 (UTC)[reply]

Feel free to restore the call, if you think an expert will answer. Being only slightly familiar with the theory, I cannot supply such material. Theory has been better addressed in the sideband and modulation articles, and perhaps the present article needs prominent links to those and others that can fill this need. If this article fills out with good theoretical material, we can move down the antique phone material and more modern applications to an "applications" section or to a separate article or articles.

Heck, if I wanted to take the time and a little study, I could write an article this size merely on telephony FDM. But until someone wants to supply a good treatment of the hows and whys, as distinct from the theoretical treatments in related articles, I see no reason to do any of this. But then, I'm saying all this from the POV of my own limits of knowledge. There are plenty of people who know better, and they can do better and I'd be all in favor of it.

Why not give it a try? Write a brief sketch that introduces what you want, and make it Section 1, moving the application sections down deeper into the article. Perhaps such a start will attract the kind of expert we need, better than the flag that stood at the top of the article for months without avail.

Oh. I took a brief look at your personal page. You've definitely got the education; I'm just an old grey-beard telephone mechanic, and didn't even work on FDM signals when they were in use. Why are you calling for an expert? You should be able to write a brief and elementary introduction to FDM theory. If you like, I can serve as test subject; if your explanation is too abstruse for me it's probably not suitable for the majority of Wikipedia readers. Teamwork is what makes Wikipedia work, as far as I see.

Jim.henderson 19:03, 13 November 2006 (UTC)[reply]

Trivia: Alexander Graham Bell invented frequency-division multiplexing. His telephone patent included a means for multiplexing telegraph signals. He called it the Harmonic Telegraph. 69.22.22.161 00:43, 17 November 2006 (UTC)[reply]

Call for split[edit]

Thinking about it for a couple months, I have come to like the idea of splitting off the telephone section (except for a new sentence or two and a link). Since the diagrams are of the "A" type channel bank that were used with the Bell System L Carrier system and the microwave chains, I propose to name the new article "L-carrier" in imitation of the existing T-carrier article. Alternate names could be "Channel bank" or maybe "A Bank" unless someone comes up with a better idea. Actually more of these A banks were used with TD microwave than with co-ax, and a fair amount of the co-ax was working outside the USA and thus not using the "L" name, so maybe another article name would be appropriate. Especially, moving this material into an existing article would be nice if an appropriate article exists. Anybody got a suggestion or preference? Jim.henderson 07:52, 9 February 2007 (UTC)[reply]

Someone needs to add other common FDM systems[edit]

I am an electrical engineer who has worked my entire professional career for or with telephone companies and cable companies or their equipment vendors. I like that the article includes the old analog FDM telephone channel multiplexing hierarchy. However, at the very least CATV (NTSC and PAL) and radio (AM and FM) should be mentioned for this to be a general article on FDM. I'll add some of that general material myself when I have some more free time. — Preceding unsigned comment added by 72.152.236.157 (talk) 19:18, 12 May 2012 (UTC)[reply]

British Rail used FDM for safety critical signaling control systems (Reed FDM Remote Control) in the 1970s and 1980s over three generations - the kit is still out there in use, although the allowable selection of frequencies is somewhat reduced. — Preceding unsigned comment added by Dengieite (talk • contribs) 15:28, 11 November 2014 (UTC)[reply]