What the heck are these plugs for?

A link would be nice, but I've seen plugs like what you're describing used for plug in keyboards, controllers, and even small power supplies - anything that needs a quick disconnect.

I needed to replace a 1/8" stereo plug on a cord. I found on ebay a pack of three 1/8" stereo plugs from China, for about $2. I dont normally order from China, but for the price and since I was in no hurry for them, I bought them.

That was a mistake. They are NOT stereo, they are THREE CHANNEL. The tip of the plug has THREE contacts, (plus the grounded base). What the heck are they for? I have never seen any 3 prong 1/8" jacks on anything.

Yea, I could just ground the uppermost terminal so it acts as a stereo plug, but it gets worse. Under the shell, I found a solder on ground contact. But none of the three conductors have any contacts attached to them. There are just three pieces of "rod" sticking out the back, with the insulation in between. I would have to wrap the wires around them, and solder them and by the time I manage to do all that in that tiny space, I'd probably melt the insulation between the sections and unless they wires were hair thin, they would short against the ground terminal.

For the small price, I am not gonna make a big deal out of it. I'll just have to order some properly made plugs from an American manufacturer, and use these worthless plugs for a conversation piece.

You find these on things like headsets and mobile phones where you have stereo audio plus a microphone down the same cable.

Gareth.

You seem to have bought TRRS rather than TRS plugs, mobile phones often use them for stereo headsets with mic (and sometimes answer/end call buttons, or FF/REW buttons)

I've also seen them on X-Box headsets now that I think about it.

They are for cell phone headsets and other connections to a phone (like a car). Left and right audio out, and microphone. Blame Apple.

Jon

Not hardly, people don't think of 10 inches as 0.833 feet nor do they think of 10 feet as 3.333 yards.

What do they think of feet and yards? To me a yard is *about* a meter and a foot is 0.3 meters.

Wrong. You're creating more digits than was originally intended by adding spurious significant figures. 10 inches has only two significant figures. Therefore: 10 in = 0.83 ft = 0.00016 miles = 0.57 Roman cubits and so on.

For domestic consumption, I use US units. For scientific, I use metric units. For political discussions (i.e. AGW) or when I want to confuse the reader, I use SI units. When dealing with government agencies, I use the same as what they prefer, which are usually units of measure that have been aged for at least 100 years. For Usenet discussions, I use a wide mixture of these, to insure that my assertions and guessing cannot be verified.

Jeff Liebermann wrote on 7/2/2017 1:19 PM:

I see you attended the same school as my chemistry lab professor. "Significant digits" is an idea that is very dated and was only useful when performing the simplest calculations like the ones we did on a slide rule. The real issue is accuracy. I can measure 10 feet with an accuracy better than a sixteenth of an inch (yeah, I said sixteenth because that's how my tapes are marked off) and I will still note it as 10 feet.

When I perform calculations I want to preserve the accuracy of the result, so the calculations are done with a higher degree of accuracy than the initial data. How much more accuracy should be used depends on the extent and nature of the calculations. One subtraction of large numbers can result in a small number which does not have nearly as much accuracy as the initial data. Add to that lack of accuracy with limited precision intermediate representation and you can end up with pointless data.

I would also point out that in both cases the final digits repeat. There is no way to show a vinculum in ascii so seeing repeating digits at the end of a fraction is a clue. There is nothing wrong with specifying the conversion exactly. 10 inches is 0.833 (vinculum implied but not shown). Leave it off and you *add* to the initial error.

Probably. The standard lecture was to pace off some distance ending up a bit short. One then measures the remaining distance to a much higher degree of precision. Take the number of paces, multiply by 1 yard/pace, add the precision measured distance, and the sum is a fairly useless number.

How accurate can the average tape measure wielding reader measure 10

inch or 0.0625 inches, your actual distance would land somewhere between 9.9375 and 10.0625. This does not mean that your tape measure is accurate to 1/10,000th of an inch. To be accurate, one needs to specify the measurement tolerances, as is common on all mechanical drawings and an amazing number of schematics that still display tolerances.

Using a steel rule, if you're able to measure the required 10 inches

number of spans of my index finger between the first two joints.

Argh. I sometimes see that in parts drawings. Some newly minted mechanical designer grinds out every dimension to whatever number of digits he has his calculator configured, and then doesn't bother providing a usable tolerance. The result is the machine shop doesn't

less. Such excess precision tends to dramatically raise parts costs. If you want to preserve your accuracy on your own design notes, that's fine. Just don't submit those numbers to anyone that has to make or price the part.

Yep. That's roughly what I've been mumbling about.

Very true. The convention is to round off anything that ends in 5 to the next higher digit. So, 0.8333333333 will round off to 0.833 or 0.83 or 0.8 and: 0.8666666666 will round off to 0.867 or 0.87 or 0.9

Lol. Reminds me when I got criticised for mixing metric & imperial in a technical drawing. Widget A was normally supplied in imperial units, widget B in mm, so it was the sensible way to go. But bigco bs ruled, causing extra work to be done.

NT

Chuckle. Sounds very familiar. I haven't mixed dimensions on a technical drawing yet, mostly because I usually have someone else do the work. However, a few months ago, I gave an ill prepared and short notice talk on radiation measurement, where I managed to mix the older conventional units of measure (Curie, Rad, and Rem) with the new and not so improved SI units (Becquerel, Sievert, and Gray). Audience confusion was averted by me having a conversion program running on my tablet, where I was able to rapidly supply numbers in both measurement system. I'm fairly functional in both systems, as is evident by being able to make the same mistakes in both systems, but forgot that others have their personal preferences.

Actually, there's a 3rd system of radiation measurement that I fortunately didn't mention. Health physics uses electron volts (eV) or sometimes joules to measure radiation dosage.

In my area of expertise, the RF industry has resisted pressure to name units of measure after notable dead scientists and instead uses fundamental units and ratios. It sometimes gets a bit complexicated, such as RF field power, density, intensity, etc. I have a handy cheat sheet available to keep me sane: That audio industry does much of the same with various dB over some reference level measurements (dB, dBm, dBw, dBC, dBA, dBi, dBu, dBmV, dBV, dB/uV, dBrn, dB-SPL, dBrnC, etc). More:

I could be wrong, but I think I read somewhere that the Brits used to use similar plugs for their (landline) phones. Think they called it, "plug-and-jack (or -socket)?"

Back in the day, Bell System phones were 4-wire, and all 4 had some function. Most of the world (back then) used 4 wires - Poland, apparently, used 5.

Peter Wieck Melrose Park, PA

The Bell System used two wires for the phone line and if you had a Princess phone the other two were used to supply power for the lighted dial. Otherwise the other two were for your second extension line. This has nothing to do with the four way plugs and jacks the OP is talking about.

ss

Bell System:

Up to 1930 - three active wires: Voice/Ringer/Ground From 1930 well into the 1960s, up until touch-tone *in some regions* and wi th some providers: Four active wires: Voice/Ringer/Side-Tone Suppression/Gr ound

At some point, the side-tone suppression function was served by a small cap acitor - this took a few years to become universal. A diode allowed all fun ctions to be handled by only two wires. After which the additional wires co uld serve such niceties as lighting. BUT - those functions required a local wall-wart type power-supply feeding a jack for proper distribution.

Peter Wieck Melrose Park, PA

Hello!

nit conversion app that I'm releasing a new version of, and I thought I'd s ee if people around here would like to test it.

(but don't, it make them mad).

.com/apps/testing/appinventor.ai_RoyceGrey.Frank_Harr_s_Conversion_App