# Talk:Multiplexer

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## Spelling

My understanding of the word "multiplexor" was that it was derived from "multiple" and "xor", hence it should be spelt "multiplexor" rather than "multiplexer". It seems that every article in Wikipedia on multiplexing is either spelt incorrectly, or I'm completely wrong. Any comments? mgwalker Nov 7, 2006.

Actually, it seems wiktionary agrees, labelling "multiplexer" as a "variant spelling of multiplexor". Encarta on the other hand considers "multiplexor" as "another spelling of multiplexer" (but then who trusts Microsoft to get anything right?). The Oxford English Dictionary claims "multiplexor" pre-dates the use of "multiplexer" (the first usage examples differ by 4 years). Is it appropriate to comment in the article on the spelling of this word? mgwalker Nov 7, 2006.
You might be right on the multiple-xor part. But most major institutes and books follow the spelling 'multiplexer', based on the word 'multiplex'. If you take a look at the page of definitions offered by Google, This page you'll find that the meaning of the word 'multiplex' closely matches with what we're trying to put forward in the article. Either way, 'multiplexer' is the more commonly used out of the two. Also, even if someone searched for 'multiplexor', we could hitch a redirect to handle that.

I vote we let the article be as is. Xcentaur 16:16, 7 November 2006 (UTC)

## Mainframes

I'd like to know whether multiplexers are used in main frame computers. If yes, Can they be used to increase their performance?

## N x M Multiplexer

The concept of an N x M Multiplexer came up in one of the other articles (Nonblocking Minimal Spanning Switch). Should it be added here or made a separate page? If it is made a separate page what shoul;d it be titled? RJFJR 22:35, 2 October 2005 (UTC) Uxbridge November 24 2005

## ascii art

i hate it when people use unnecessary ascii art. we have tables and TeX for this junk

I tried making a table from it, it doesn't look as good as the old ascii art one, so i junked it. I dunno if TeX would work for that either. It looks to me as if a picture is the only alternative. The ascii art in this case works decntly well. Fresheneesz 04:29, 27 March 2006 (UTC)
Seems to me if you have a problem how the art is done, n think there's a better way, then you should make it yourself and submit it as an alternative. Ark-N-Jel (talk) 07:11, 11 February 2013 (UTC)

## Reading muxs

Given a specific MUX, is there a systematic way to interpret the output? For example, in a 2:1 MUX, with first input being 1 and second input being 0, and the first sel being a, and second sel being b - is there a way to determine a single output solution? Fresheneesz 09:51, 10 March 2006 (UTC)

Yes, and its based on the conventional order of variables in a truth table. This page should show that the inputs are "input 1" at the top, and increase sequentially downward (in the pictoral representation), and that if "sel" = 1, the mux chooses "input 1", if "sel" = 410 = 1002 then the mux chooses "input 4" etc. Fresheneesz 10:38, 15 April 2006 (UTC)

## general mux

There should be a pic and eqn for a general mux. The eqn is ${\displaystyle Out=\sum _{k=0}^{2^{n}-1}m_{k}I_{k}}$ and this corresponds with a ${\displaystyle 2^{n}}$ to 1 mux. Fresheneesz 21:51, 15 April 2006 (UTC)

## what is a multiplexer?

This page says its "an encoder that combines two or more inputs into a single output.", however I don't think this is specific enough. Any encoder that has two or more inputs and a single output is a multiplexer? I think not.

The article also says: "In digital signal processing, the multiplexer takes several separate digital data streams and combines them together into one data stream of a higher data rate.". In my "digital design" class, we were not taught this aspect of a multiplexer, and thus I doubt its validity. I was taught that a multiplexer works like a switch (as all the pictures seem to indicate).

If all these definition are true, this article does a very bad job at explaining why and how the separate definitions relate or do not relate. Please someone help me fix this page. Fresheneesz 03:44, 17 April 2006 (UTC)

A multiplexer is not a switch. It combines all the inputs into a single stream and then transmits it in the channel. Whereas a switch just diverts or redirects a single signal to its destination. A switch does not combine the stream and it handles one input at a given time. But I am not sure of the word "encoder" used by the author. I checked in a lot of web resources and the appropriate term used was "combine". —Preceding unsigned comment added by Mohanramkumar (talkcontribs)
The definition changes depending upon your domain. You are speaking about a DSP multiplexer. But, in digital circuits...see http://www.phys.cwru.edu/courses/p203/resources/74157.pdf and tell me that is not a switch. There is not rate converter or anything to accomplish what you speak of. Cburnett 03:37, 12 November 2006 (UTC)
When I saw the animated picture show the lines apparently switching from one terminal to the next, it gave me the impression as well, that this was some kind of switching device. I am not claiming this is proof it is a switch, just that there defiantly needs to be more clarification. In fact it seems to me that this is written in a way that to understand it, you would have to already have a level of technical training that would likely include this information. (You have to already know it to understand it). Ark-N-Jel (talk) 07:32, 11 February 2013 (UTC)

## 128 bit multiplexer

is there 128 bit multiplexer available in the market?????? if so please tell me (santhanakrishnan_1985@yaho.com)

I assume you mean a 128-to-1? A bit in this context doesn't mean much to me as a bit requires some sort of time or spatial bounds of a logic high to make sense. A multiplexer doesn't even have a clock. Anyway, there is not a 128 input multiplexer that I am aware of.
You could "easily" make one with eight 16-to-1 and an 8-to-1. Put the selector pins for the eight 16-ot-1's in parallel and the last three selector pins to the 8-to-1 with the output of the eight 16-to-1's into the 8-to-1. What you lose in this is an increase in propagation time therefore a reduction in maximum operating frequency, not to mention you're talking 9 multiplexers but you are wanting something rather extraordinary. Cburnett 03:46, 12 November 2006 (UTC)

## Enable signal effect

One solution is to add an enable input to a MUX. When the enable is active, the output is selected from one of the inputs. When the enable is not active, then the output is Z. (From a link in Tri-state_buffer)

Does the enable line always cause high Z outputs? If not, what use is it?

not really. enable input is primarily to decide whether or not you want the mux function at that time. meaning, you can disable the mux as required. this has applications in 'cascading' multiplexers, like making a 8:1 from two 4:1 mux. I was going to add this to the article, but i've had exams...... once they get over, ill add that section asap 8) -Xcentaur 15:20, 13 November 2006 (UTC)

## Truth Table Heading

Shouldn't the truth table headings be S A B Z rather than S A B C to correspond to the equations in the paragraph. Cgantz2000 00:56, 2 January 2007 (UTC)

## "Demux" in a Digital Video Editing context

I would like to see what demux means when used in relation to digital video editing. My guess is that it means two take an movie file and save a copy of one of the streams (E.G. take a video file with audio and save a separate copy of the audio). I went to Wikipedia to double-check my definition, but alas, no info here about that term in a video editing context. -- Eptin 21:50, 14 January 2007 (UTC)

Yup. Multiplexing combines streams into one (any number of video and any number of audio) and demux is the opposite, but not necessary "saving" the streams. When playing a file it is demuxed to video and audio and played accordingly, for example. Cburnett 22:03, 14 January 2007 (UTC)
This particular article is all about electronic multiplexers, so it shouldn't be getting into other types of multiplexing. I've just updated the more general multiplexing article to introduce the terms muxer and demuxer and describe that type of computer software appropriately. See Multiplexing#Video processing. —mjb 20:11, 17 July 2007 (UTC)
The problem with that is if you are working with video editing and want information on demuxing, you're redirected to this article so ignoring "other types" is not a solution. Of course this kind of confusion is commonplace in the English language. Mostly because the people who establish the "proper use" of words or terms seem to have no imagination or initiative.
This is a perfect example. The obvious solution is that these terms need to be separated rather than being used interchangeably. Multiplexing, etc. should be reserved for use when describing electronic multiplexers as in in this article, while muxing/demuxing, etc. should only be used in reference to video encoding thereby eliminating the confusion. Ark-N-Jel (talk) 04:11, 11 February 2013 (UTC)

## Electronic Component Symbols

In many books, the symbol for a demux looks exactly the same as a mux, except it is rotated by 180 degrees. Meaning, the narrow end of the symbol always has 1 terminal and the wide end has 2 or more terminals. On this wikipedia page it, it always treats the narrow end as an output for both symbols. Is there some sort of standard demux symbol? —The preceding unsigned comment was added by 69.64.217.18 (talkcontribs).

I've only seen what you describe and I agree that
is backwards. I shall add making an SVG demux on my list. Cburnett 16:02, 2 February 2007 (UTC)

## Digital Multiplexors: 2-to-1 Multiplexor

The current line reads "A straightforward realization of this 2-to-1 multiplexer would need 2 AND gates, 2 OR gates, and a NOT gate." Shouldn't it be 2 AND, 1 OR, and 1 NOT? I don't see where the second OR gate would be used...

Sorry I'm not logged on my bad but its CPrussin —Preceding unsigned comment added by 68.57.66.15 (talk) 23:09, 1 March 2008 (UTC)

Yes. Cburnett (talk) 23:17, 1 March 2008 (UTC)

## Merger proposal

A merge was suggested between Multiplexing (which today only is about telecommunication aspects of the word) and Multiplexer (today mainly about electronics and signal processing aspects, but with a few words about communications).

• Against. As in the case with Bandwidth (computing) and Bandwidth (signal processing), there are important distinctions between a multiplexer in digital design and a multiplexer used for sending multiple signals over one channel or frequency band. The two concepts overlap, just as they do with bandwidth, but are used to emphasize different things. CosineKitty (talk) 17:44, 21 June 2008 (UTC)
• Against, since multiplexer is a physical device and multiplexing is a process. Both are totally different. I'm also against renaming either articles. jaideepster (talk) 19:15, 22 September 2008 (UTC)
• Against. Applies to different scenarios, and uses different technologies. -- Highwind888, the Fuko Master 05:39, 16 October 2008 (UTC)

That's a no then. I shall remove the merge template. --catslash (talk) 20:28, 8 September 2009 (UTC)

## Rename proposal

Any comments on my rename proposal above?

Could potentially be useful for some of the pages in the see also section to be put into a disambiguation page... -- Highwind888, the Fuko Master 05:42, 16 October 2008 (UTC)
• For. I came to this page expecting it to be about telecommunications, but was disappointed. The proposal would fix this. --catslash (talk) 12:36, 1 June 2009 (UTC)
• For I also came to the page expecting it to be about telecoms, and was disappointed. Perhaps Multiplexer (electronics) and Multiplexing (telecoms) would work best as main page titles with redirects from the other options. But would this change mean you had to write Multiplexing (telecoms) every time you want to refer to the new page? Opticalgirl (talk) 12:25, 26 August 2009 (UTC)
Yes, you have to write that when creating a link to the page, but you can use a pipe to make it appear to the reader as just multiplexing (or whatever you want).--catslash (talk) 18:36, 29 August 2009 (UTC)
• For. This article is too general, keep the general content here (same name), but also create separate pages for suggested topics above, moving specific content from here to those new pages. Hatnotes will help in further navigation. --IncidentFlux [ TalkBack | Contributions ] 13:06, 26 August 2009 (UTC)

## Multiple Output Multiplexers

Shouldn't the definition include multiple output multiplexers? Shouldn't there be a section with an example, perhaps of a 4X2 multiplexer? fogus (talk) 00:34, 4 December 2008 (UTC)

Well, first I'd assume you have a few sources with material to abstract from. Tedickey (talk) 00:54, 4 December 2008 (UTC)

## Practical Purposes

Aren't multiplexers used in karaoke to remove lead vocals? This article needs a Practical Purposes section to describe what they are used for.174.92.44.54 (talk) 18:53, 7 February 2010 (UTC)

Sounds more like a "popular culture" item. The topic does tell what they're used for. Tedickey (talk) 19:11, 7 February 2010 (UTC)

## help

Now it is asking if one were to do it via a multipxer for Jd and Kd thru Ja and Ka and each gerated by using a multiplexer that is a 8 to 1 line multiplexer for each J and K controll. it says to write down the 8 input lines of each multiplxer, including alternatives. It says the least significant address lines is the ones and is connected to Qa and the most significant the fours, adress line is for each multiplexer is Qc. It states that Qb is connected to the twos adress lines in each case.

please helpDoorknob747 (talk) 16:29, 25 March 2015 (UTC)

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## Watch out for race condition

The logic given for the 2-to-1 mux is mathematically correct. However, a direct implementation with physical gates would encounter the problem that S and S̅ can change at different times due to delay across the NOT gate. If S changes from TRUE to FALSE while A and B are both TRUE, a FALSE glitch can occur at the output. It's not necessary to go into the details in the article, but I have added a note. 24.7.14.87 (talk) 07:27, 13 May 2016 (UTC)