Wikipedia:Reference desk/Archives/Computing/2016 July 8

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July 8

Shared speakers ?

I have several sets of speakers (mostly "2.1" systems), for various TVs, computers, radios/CD players, etc. I was wondering if it would be possible to plug all the devices in one room into the same speakers. There would be the physical problem of splicing the lines together, then issues of the devices interfering with each other, especially if more than one was on at a time. They might also have different plugs, impedance/resistance, etc. So, is this possible ? Would it only work with a physical switch to connect only one at a time ? StuRat (talk) 01:04, 8 July 2016 (UTC)

Hang on you want to connect several devices into ONE set of speakers or into SEVERAL sets of speakers all at once? Vespine (talk) 04:46, 8 July 2016 (UTC)

Sorry after reading it multiple times I think I got it. You want to get rid of several sets of speakers and just use one set for everything. Yes this will work, but does depend on several things. Whether you get ground loops happening with all the equipment running straight into your speakers would be my biggest concern. The "real" solution is to get a mixer, which I don't think there's really any super cheap option, starting at about $50 for a 4 stereo channel mixer. Vespine (talk) 04:59, 8 July 2016 (UTC)

Thanks. Would I then need to manually select which channel(s) I want to hear, or would it be smart enough to only select the channel(s) with a real signal (as opposed to static) ? StuRat (talk) 16:08, 8 July 2016 (UTC)

You would need to do it manually, unfortunately, it's a very steep step into "pro audio" territory. You need something like a gated automixer, but i don't think there's such a thing as a consumer version of such a device so you probably won't find a cheap one. Ideally, you would have an AV receiver, if you keep an eye out, you might be able to find a cheap 2nd hand one, if you are lucky maybe you'll find one where the "video" part is broken and just use it for the "audio" part? I've had a quick look at a classified website and there's loads for $50. Mind you they're pretty huge so if you are short on space it's probably not the best solution either... Vespine (talk) 00:00, 11 July 2016 (UTC)

Thanks. I was just wondering if there was a way to simplify my life and combine all these speakers into one. These days flat screen TVs and computer monitors all have built-in sound that totally sucks, so now I have a plethora of these 2.1 speaker systems, one for each device. That gives me decent sound, but the clutter is bad. StuRat (talk) 03:17, 11 July 2016 (UTC)

How do I print the arithmetic mean symbol, "x bar", in Microsoft Word?

The symbol for the arithmetic mean is called "x bar", which is the letter "x", italicized (I believe), with a bar over the "x". You can see it in this article: arithmetic mean. My question is how do I get that symbol to print in Word? I looked through all of their symbols on the "Insert" tab. They have a million odd symbols, but I can't find this one anywhere. Thanks. Joseph A. Spadaro (talk) 03:22, 8 July 2016 (UTC)

This is the symbol: ${\bar {x}}$ (read $x$ bar). Joseph A. Spadaro (talk) 03:24, 8 July 2016 (UTC)

First, start the equation using Insert Equation. Then type the "x", select it, and in the Equation ribbon, select accents, and choose the bar. This instruction comes to you courtesy of Googling "type x-bar in Word".--Shantavira|^{feed me} 06:36, 8 July 2016 (UTC)

Thanks. But, I don't want an equation. I just want the symbol. Is it not available as a regular symbol, like the dozens of others? Joseph A. Spadaro (talk) 07:57, 8 July 2016 (UTC)

They have millions of symbols that I am sure no one ever uses. But they don't have a relatively commonplace symbol like the x-bar? Joseph A. Spadaro (talk) 08:01, 8 July 2016 (UTC)

@Joseph A. Spadaro: There are actually two parts in that question; one, how does Unicode provide a symbol for x̄, and two, how does one write it in MS Word.

Going by [1] (which includes a detailed procedure in Word at the end) there is no single-symbol "x bar" in standard Unicode, but some fonts accept diacritics so that you can effectively get what you want with "an x, with a bar over it". You will need to make sure the font supports it, and you will need to find the diacritic, but it works. Tigraan^{Click here to contact me} 09:11, 8 July 2016 (UTC)

@Joseph A. Spadaro and Tigraan: Possibly the Unicode U+0305, called a 'combining overline' is what you need; see Overline. --CiaPan (talk) 09:24, 8 July 2016 (UTC)

In MacOS with the Extended keyboard setting, option-shift-a (after the base letter) makes U+0304 COMBINING MACRON: x̄. —Tamfang (talk) 09:27, 8 July 2016 (UTC)

Doesn't Word have the option to add an overbar in character format? So, you type an italic x and add an overbar. Done. 209.149.113.4 (talk) 14:49, 8 July 2016 (UTC)

Thanks. Let me change my question. When I look at the symbols available in the Word "Inserts" tab. they have hundreds upon hundreds of extremely esoteric symbols. (Many of which are odd and bizarre. Many of which are useless, like "cute" little drawings.) Stuff that I am sure no one ever uses. Why would they not have a relatively "common" symbol, such as the x-bar? Thanks. Joseph A. Spadaro (talk) 17:57, 8 July 2016 (UTC)

You'd have to ask the Unicode Consortium about that. Presumably, x bar isn't included because it can be created by combining two pre-existing symbols as shown above. clpo13_(talk) 18:56, 8 July 2016 (UTC)

If you ask for ${\bar {x}}$, other people will ask for ${\bar {y}}$, ${\bar {M}}$, ${\bar {\theta }}$, etc... Mathematically, it is more appropriate to think of the bar as a modifier of whatever variable you have, whether it's called $x$ or anything else. --Wrongfilter (talk) 20:01, 8 July 2016 (UTC)

That could be said of many other symbols they already do include. Joseph A. Spadaro (talk) 20:13, 8 July 2016 (UTC)

You may want to read Precomposed character. Basically, combining characters are preferred since they are much more flexible (you can put a COMBINING OVERLINE character on almost any other character, while with precomposed characters you're limited to what's available). But some older software has trouble handling combining characters correctly, so they added some precomposed characters for what they considered to be common cases. x-bar apparently wasn't one of those cases. CodeTalker (talk) 00:06, 9 July 2016 (UTC)

Correct. And it wasn't just "what they considered to be common cases"; in general they included characters (that is, single-point or "precomposed" characters) only if they had already been included in ome other notable character set. (That is, they didn't trust their own judgement; they applied something similar to Wikipedia's Reliable Sources policy.) —Steve Summit (talk) 15:59, 9 July 2016 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 04:28, 9 July 2016 (UTC)

Looking for a pointer

On Windows 7 (64-bit) every time I leave the PC for a while the mouse pointer disappears. Wiggling the mouse doesn't bring it back, but CTRL-ALT-DEL does, and it remains after I hit the Cancel button. What causes this and how do I stop it ? Note that it doesn't appear to have gone into sleep/hibernate mode, as the original screen is still displayed (not a screen saver). StuRat (talk) 18:03, 8 July 2016 (UTC)

Have you done virus checking firstly? -- Apostle (talk) 18:10, 8 July 2016 (UTC)

The physical interface is acting as if the screen locked. I have seen screensavers fail such that the screen locks, but the display doesn't change. So, you have to blindly unlock the screen - which can be difficult if you have to ctrl-alt-del and then type a password. 209.149.113.4 (talk) 18:21, 8 July 2016 (UTC)

UPS

1. What brand is highly praised?
2. Do they come with Lithum ION battery (or something better) like the Laptops? Does a UPS protect itself from ‘electric over powering’ the battery, like the Laptops which consist of circuts to mitigate over powering the battery…?

Apostle (talk) 18:08, 8 July 2016 (UTC)

It isn't a brand thing. I assume all brands make good and bad products. I have an APC 1500. It has been great. I also have an APC 650. It is crap. The output is so flaky that it sends my computer into power fault every few hours. So, I stopped using it. They do have circuits to stop charging the battery when it is fully charged. That should be obvious. Otherwise, a UPS would be pointless because you'd have to unplug it when charged and, somehow, plug it back in very quickly just before power goes out. 209.149.113.4 (talk) 18:28, 8 July 2016 (UTC)

They usually use lead batteries. Ruslik_Zero 20:34, 8 July 2016 (UTC)

Noted, and thank you both. Sorry for the delay, I was unwell. -- Apostle (talk) 18:07, 10 July 2016 (UTC)

Sectorless or blockless storage

Is it possible for memory storage, either magnetic or flash, without sector sizes or block sizes to exist? I am imagining an EEPROM that has no blocks. Would the construction of such be more difficult. — Melab±1 ☎

Read the flash memory article. NOR flash is byte-addressable. However NAND is cheaper and can achieve greater density, so it's typically used, unless the characteristics of NOR flash are needed. As for hard drives (which usually aren't referred to as "memory"), blocks are used in modern drives because the drive calculates and stores ECC for each block. This is a consequence of cramming data into such small areas. The signal is very weak, and read errors are a frequent occurrence. --71.110.8.102 (talk) 23:39, 8 July 2016 (UTC)

All NOR flash I've seen was divided into blocks just like SD cards are divided into sectors. The connection between "modern drives" using "blocks" instead of sectors due to ECC is dubious because other storage that uses "blocks" has no ECC (I haven't seen a hard drive that uses blocks, anyway). — Melab±1 ☎ 20:00, 9 July 2016 (UTC)

Maybe I'm missing something, but I don't see where it was claimed hard drives use blocks instead of sectors. The claim seem to be that hard drives are in blocks or sectors instead of being single byte addressable. Sector is arguably the better term to use for the physical chunks on hard drives since blocks often refers to the chunks used by the file system, Disk sector#Sectors versus blocks [2]. Still I don't know if you can say the usage is explicitly wrong. After all, consider Logical block addressing and Block (data storage). (Although as 512e shows, LBAs and presented sector sizes don't have to correspond to physical sector sizes. And nowadays we have the Shingled magnetic recording hard drives to complicate things even more when you consider writing.) Nil Einne (talk) 13:39, 11 July 2016 (UTC)

There are implementations that do not use addressable memory. I worked on a system that used track memory. A large rotating drum had a spiraling track that went from one end to the other. When a signal arrived, it was placed on the track at the current location of the head. If there wasn't an incoming signal, the head would read whatever track information was written and send it out as a repeating signal. It was, in effect, a repeating analog buffer - but it was memory and it wasn't broken into blocks or sectors or bits or addresses. It had a good use in that one particular case, but is rather useless for a modern computer. The argument to make is where the concept of "memory storage" ends. Is it memory storage if you are recording analog signals? Does it have to be binary? Is an old vinyl record memory storage? 209.149.113.4 (talk) 12:27, 11 July 2016 (UTC)