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Black Boxes

By Bruce R.

I bought a new cell phone. Part one of the problem. It had a 3.5mm headset jack. Huh? I had a 2.5mm headset. So I needed an adapter or another headset. I went to Best Buy. Yup, it's a new standard.

Here's the setup, so that you can understand this from the non-black-box perspective, that an electronics geek would know.

The new standard is logical, because the old head set was just one ear piece and a mic, so 3 conductors are needed, and they used a standard 3 conductor "mini" TRS stereo plug (Tip, Ring, Sleeve). The sleeve would be the common ground (or shield) for the mic and the ear. Apparently the tip is usually used for the ear piece and the ring for the mic.

Now let's make things more interesting. iPhones and other "smart" phones wanted to output stereo AND have a mic. I.e. you could plug in a regular headset, or stereo headphones. The phone would sense if the "ring" connector was a mic or a speaker, and adjust. Still this is somewhat intuitive, because no one expects to talk into their headphones. From the blog discussions, it sounds like they were still using the 2.5mm TRS plugs.

But users do not want to switch between a headset and headphones. So they came up with the stereo headset idea. But now there are two design choices: use a switch, or add another conductor.

The switch option would switch between the headphone or headset modes. Modes are BAD for user interfaces. Don't believe me? How many people do you know, who really understand how to use the "Tape" mode button on their preamplifier? "The stereo is broken" my family members would moan. I would just glance at the pre-amp, and push out the tape button. Or if I was feeling less mean, I would haul out the unit, and wiggle all of the wire, and grumble, then fiddle with the front switches. (Reminds me of auto mechanics. Now I make sure to praise and tip mechanics when they find something simple! And to never utter "well duh".)

So for the non-mode option, you need 4 conductors, which means you need a TRRS plug (Tip, Ring, Ring, Sleeve). They made a short lived mistake of using 2.5mm TRRS plugs. Confusion" "my old headset doesn't work, and my old headphones are mono". Duh. So they switched to a 3.5mm TRRS plug. Good for them problem solved.

Not so fast buster! (Part two) I have other "old" devices that I would like to plug into that handy stereo headset jack. You are not going to make me buy new devices, when I know there is a simple solution. For instance, I have a 2.5mm stereo plug in my car, which connect to a cassette tape adapter, so that I can us my mp3 player with my car stereo. Now I can replace the mp3 player with my cell phone. I also have some really comforatable headphones.

So I just need a "3.5mm TRRS male to 2.5 female" adapter, that will be audio out only. Guess what, no such thing exists (well an hour or googling didn't find anything). And I know why. The engineers went to so much trouble to come up with a solution that has no modes, the last thing they would want would be an adapter that did not support the full headset functionality. It also doesn't make business sense, because people are now trained to expect full funcionality, when they buy and "adapter", they expect it will work with all the old devices. But most people will only be using their old headset (the ones with a mic). So there are adapters that will support the old 2.5mm headsets, but there are no stereo headphone adapters.

Fine, I'll build my own. Radio Shack had no 3.5mm TRRS plugs! Fine, I'll order one online--at least that is still possible. With some fiddling, and the use of an ohm meter, I can figure out the pin connections, but it would be nice to have the actual wiring directions. So I googled for that. Wikipedia was a joke. The "geek" sites had lots of discussions about existing adapter problems and almost nothing about how to make your own. An audio engineer had a good rant about what the "usual" standards were, and it appears that HTC (my cell phone's manufacturer) swapped things around.

So here is what prompted me to write this long-winded essay: One of the posters was desperate to get an adapter that worked, so he took a 3.5mm headset and cut the wires and then, with trial and error, figured out what wire was what. Good for him! But then he posted in detail the color codes of the wires:

> solid red = right +
> striped red = right -
> solid green = left +
> striped green = left -
> white insulated = mic +
> copper (unpainted) = mic - (common ground)
> blue = call/answer/reject/redial button signal wire

Sounds useful. NOT! What is the exact manufacturer and model for the headset? Even then, the same manufacture can change their wire vendor at anytime. The color coding of audio is no where near as standard as RJ45 CAT5 or CAT6 Internet cable standards. He even admitted that he didn't know which wire went to which ring or tip. Dufus, that is the only thing that is worth posting! Get your VOM and do a trivial continuity test (he obviously has a VOM, because he noted +/- for the wires). Oh, and the manufacture/model of the cell phone matters too, since there seems to be no standard for the 3.5mm jack.

Obviously some deeper digging might get me to some sites with people who really understand the details that matter. But the top google hits all lead to blog sites where the discussions are equivalent to listening to little kids trying to figure out how TV's work. But these blogs were about some simple little pre-made jacks and plug adapters--things that I was making when I was 10 years old.

Of course everyone will have a "black-box" that will stump them, while others will look at them with a big "duh, you don't know how that works?!". Ask me about how RNA fits into the DNA process of cell replication. I'm such a dufus in that area, that I probably haven't even phrased the question properly.

Business model for the new long term local economy: make things that will last, support older HW, and follow standards (but be careful with lock-in).

Main sources for these thoughts

"Connections", by James Burke, 1978. PBS series: http://www.youtube.com/watch?v=OcSxL8GUn-g

I was in that first big east coast power outage. Excellent series. People using things that they really don't understand. But mainly the series is about how inventions happen when the pieces are all available (often in different contexts), and someone notices.

"You are not a Gadget", by Jaron Lanier, 2010. amazon.com

I highly recommend it. The Internet is not making $ for everyone, like it was envisioned. The "give it away for free, and you'll be rewarded" experiment is failing. What to do about the problem of software "lock-in"? Where is the new pop music--and why is generation X and this new generation so "bland"?

Paraphrasing one of his main points: computer technology, is stripping away our humanity in ways that are so insidious, and subtle, that most don't even notice they are being changed. Or if they do notice, they don't consider alternatives.

Another reason for recommending this book: he describes solutions, not just a list of overwhelming problems.

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