Talk:Duplex (telecommunications)/Archive 1

Archive 1

Simplex vs. Half-Duplex

I know that the article follows tha ANSI standard. Is there any documentation of how that came to be the standard? There are a couple of confusing points:

1. Using the road analogy, everyone agrees that (full) duplex corresponds to a two-lane road, with traffic flowing in either direction, each in its own lane. Half of that would seem to be one lane travelling only in one direction.
2. Similarly, two of what ANSI calls half-duplex gets you full-duplex plus a lot of overhead for managing the direction of traffic in either direction in either lane. When does two times a half equal more than a whole? In duplex communication, I guess. Maybe we could call the result double-half-duplex and confuse everyone?
3. Before duplex communication was invented, people used one line to talk to each other (say on a telegraph). It seems odd that such a system would be called half-duplex, when presumably that was just the way it is prior to duplex.
4. Nobody that did not have a duplex telegraph in mind is likely to have invented a one-way circuit, so does that mean simplex requires duplex, but half-duplex came along independently and first?

If it is possible to document why the decision was made to make the current naming the standard, it might help inquiring minds make sense of the situation. Dpv 15:15, 8 June 2006 (UTC)

Hm, all my education in electronics has always taught me the ANSI spec.

To me, "Dup-" as in "Duplex" means two. Probably why "(full) Duplex" means two-way communication. "Simp-" as in "Simplex" means simple, as in lowest working system, i.e. a one-way broadcast like TV, AM radio stations, etc. Certainly adding traffic management systems and controlling the flow over a single channel is not "simple".

"Half-Duplex" still contains the "dup-" part, so to me it means its still two-way, albeit over one channel with switching.

I don’t agree that two half-duplex channels give you full-duplex. As the entire connection (both channels) can be switched to the same direction, then to me this is simply a wider bandwidth half-duplex channel. Assuming each channel had a 50 Mbit bandwidth, you then have a 100 Mbit half-duplex system, that can transfer 100 Mbit at a time, either up or down or a combination of the two with the proviso that one can't exceed 50 Mbit while the other is happening.

Whether it is done by allocating the available channels to different directions, and switching these as needed or allocating the same channel to different directions via a TDMA protocol, then its still a half-duplex system to me. Bonding multiple half-duplex systems just gives you a finer granularity than an 'up/down' system

Calling a one-way system like TV/radio "half-duplex" to me doesn't sound right. "Uniplex" maybe?? :/

A clear term for one-way already exists and is in use: "simplex". There is no need to invent another.

--87.127.25.131 07:28, 17 June 2006 (UTC)

I know that most people are trained according to the current standards, and once trained they tend to think what they were taught is logical. My question is how the standard came to be the way it is now. It seems odd that two half-duplex don't make a full-duplex. It seems odd that the way telegraphs worked before anyone had duplex is now called half-duplex. But I know standards don't make sense to everyone all the time. (Does anyone really use their favorite term for one-way only communication, whether half-duplex, or simplex, for broadcast radio? I would normally only think of it for something like a telegraph wire with a Morse-code key on only one end and a buzzer only on the other end. "Broadcast" is a good enough term for the radio example.) I really want to know if we can explain the current terminology with documentation of how it came to be the standard. Dpv 11:48, 17 June 2006 (UTC)

"These terms also apply to early PC sound cards, however almost all are now full-duplex." - is it really still possible to buy a half-duplex PC sound card?

Incorrect and misleading edits

24.8.10.46 has made a lot of edits which are pretty harmful to this page. Aside from removing entire entire sections (there's no longer a section about half-duplex, which breaks any pages that link to that section), the new information is biased towards radio systems, and completely discounts other types of half- and full-duplex systems like UARTs and Ethernet. A lot of the new information contradicts what was previously in the article, such as claiming that "The only advantage of TDD systems is the requirement of only one channel/frequency" when multiple other advantages were previously listed.

No doubt this article could use some improvement, but these edits are substantially lowering the accuracy and quality of the article.

While it would be useful to explain the modern relevance of half- and full-duplex in radio, cellular, and Wi-Fi systems, this article also needs to consider other types of radio systems (such as family walkie-talkies, long-distance radio links, and satellite links), non-radio communications (like UARTs and Ethernet), and historical systems (like telegraphs).

24.8.10.46, your edits thus far neglect all of those, which is why I've reverted them. If you want any part of these edits to stay, you need to provide some justification for why the information you've added is accurate and improves the article. --Bigpeteb (talk) 22:11, 4 April 2017 (UTC)

I haven't studied the edits in detail, but I think I agree with you. And since the IP put them in again without joining this discussion first, I took them out again. Dicklyon (talk) 14:42, 12 April 2017 (UTC)

Some of the statements are actually pretty bizarrely off-base, probably representing the IP's own narrow experience: "Seperate uplink and downlink channels/frequencies are required." / "Full duplex systems offer all users a private/secure communications link." / "Full duplex systems unlike half duplex and simplex systems are much less susceptible to jamming." / "Half duplex systems utilize separate channels for uplink and downlink, i.e., separate transmit and receive frequencies." etc. Dicklyon (talk) 14:46, 12 April 2017 (UTC)

I agree; these are not supported by the references I've seen, and are just wrong. Support reverts by Dicklyon and Bigpeteb. The editor 24.8.10.46 has been blocked for a week for similar edits to Simplex communication. --Chetvorno^TALK 17:51, 12 April 2017 (UTC)

Lead too long?

It seems pretty right for me to say that the lead section is too long. Are there any poeple who agree or disagree? -Year1888 22:29:10, 11 March 2019 (GMT+1)

The lead is 4 paragraphs which is pretty standard. I think it's OK. ~Kvng (talk) 12:50, 14 March 2019 (UTC)

Full-duplex vs. Full-duplex emulation

Is the difference between full-duplex and full-duplex emulation the use of separate not shared mediums? --Foia req (talk) 19:24, 3 August 2018 (UTC)

Yes. ~Kvng (talk) 12:52, 14 March 2019 (UTC)

Completely omitted terms, and unclarity

The term "diplex" has been completely ommited from this and related articles.
1) In a "simplex" system, only one transmitter can send on the channel at a time.
2) In a "diplex" system, two transmitters can send on the channel at a time.
3) In a "multiplex" system, multiple (three or more) transmitters can send on the channel at a time.
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The abbreviation "TDD" cannot be used for "time division duplexing", because in the United States, "TDD" already means "Telecommunications Devices for the Deaf". I dislike it when people try to give duplicate meanings to acronyms. For example, "USA" always means the "United States of America", and there is no confusion, and likewise, "U.K." always means the "United Kingdom".74.163.48.102 (talk) 03:37, 1 October 2008 (UTC)

The list above doesn't look right. See Diplex. ~Kvng (talk) 19:17, 12 December 2022 (UTC)

Don't argue about the terms

It doesn't make any sense to discuss about which term came first, or whether "two times half-duplex equals full-duplex". These terms are historical ones that came up as the need arose, and not through some sort of a rational system. They just didn't - and we have the historical terms and continue to use them.74.163.48.102 (talk) 03:44, 1 October 2008 (UTC)

Echo cancellation

Shouldn't echo cancellation (as used by V32, etc) be mentioned here, or am I misunderstanding the page? (I can add it, I just want to be sure this page isn't intended to be specific to, say, radio technologies or something.) Squiggleslash 23:13, 2 January 2007 (UTC)

Added at some point Duplex_(telecommunications)#Echo_cancellation ~Kvng (talk) 19:28, 12 December 2022 (UTC)

Ethernet example

Full-duplex ethernet schemes are more varied than the example given in this article. Below are some methods used to achieve full-duplex operation:

10BASE-T: two simplex twisted pairs, one in each direction.

100BASE-TX: two simplex twisted pairs, one in each direction.

100BASE-T4 (rare): four simplex twisted pairs, one in each direction and two subject to negotiation.

100BASE-T2 (rare): two duplex twisted pairs with echo cancellation.

1000BASE-T: four duplex twisted pairs with echo cancellation.

1000BASE-TX (rare): two simplex twisted pairs, one in each direction.

That's just for ethernet over twisted pairs. Some of the optical standards use wavelength-division multiplexing for full-duplex over a single fiber. There's weird older stuff like 10BROAD-36, too. —Ryan (talk) 20:02, 18 October 2009 (UTC)

The 4th paragraph of Duplex_(telecommunications)#Full_duplex seems to be a good summary. I don't think we need to introduce all this jargon. ~Kvng (talk) 19:28, 12 December 2022 (UTC)