Scott Townley
Raritan, NJ

"...as much computing power as some third-world countries..."

Today's mobile devices are truly amazing.  My Motorola Bionic has a dual-core 1 GHz processor...that's more power than the desktop I currently use.

Some clever folks have written clever ham-radio oriented applications for the Android operating system.  In particular, Wolphi has apps to use your Android device as a computer terminal for decoding CW, and better yet, receiving and transmitting PSK31 and RTTY!  What more could the mobile operator ask for?

What's that hole for?

Well, they could ask "how do you connect your phone to your radio?".  And they'd be pretty hard pressed to find the answer.
TR, TRS, TRRS, bands, plugs, jacks, poles...?
Most phones have a "headphone" or "headset" jack.  Accurate information on how this jack is configured is surprisingly hard to find, and seemingly contradictory at times.  Fortunately, I can fix that.  But first, a glossary of terms.  The following pictures will help.
Plug:  the thing that "plugs into" something.  The first two pictures above are plugs.
Jack:  the thing that gets "plugged into".  The rightmost picture above are jacks.  The memory device I use is:  "Jack is female".
Pole:  a connection point, or a single conductor in a circuit.
Band:  those black lines that run across the plug.  Sometimes they are easier to count than poles.  Also known as "rings".

TS:  "tip-sleeve".  Also known as "mono".  Not shown above.
TRS:  "tip-ring-sleeve".  Also known as "stereo" or "3 pole"...all the same thing.  This is the middle picture above. 
TRRS:  "tip-ring-ring-sleeve".  Also known as "4 pole".  Nearly universally used on these confounded "smart phones".

2.5mm:  the physical diameter of the opening in the jack (rightmost picture above)
3.5mm:  same, but bigger.
A short history of portable electronic devices
When headset jacks first started appearing on mobile phones, they were 2.5mm 3 pole jacks, wired thusly:
T=microphone
R=earpiece
S=ground

When MP3 players and other small music-centric devices appeared, they were nearly all 3.5mm 3 pole jacks, wired:
T=left earpiece
R=right earpiece
S=ground

Some early high-end phones incorporated music players, and their jacks were generally the same as MP3 players (3.5mm 3 pole).  But you couldn't use a headset.  Occassionally a phone would come along that wasn't a music player, but had a 3.5mm 3 pole jack wired mic/ear/ground.  This is where things started getting confusing.

Recently, someone solved the music+headset problem by coming up with the 4 pole jack.  Nearly all headsets in use were 2.5mm plugs, so the 2.5mm jack was kept.  So that the existing base of headsets could be used, T=microphone was maintained as well.  So the 2.5mm 4 pole jack is (from tip to base):
T=microphone
R=left earpiece
R=right earpiece
S=ground
If you inserted an older 2.5mm 3 pole headset, you would get microphone, one earpiece, and ground...it worked.  But if you used a 3 pole, 2.5mm plug-3.5mm jack adapter to listen to the music player, one ear got a nice burst of DC that was intended for the microphone, and no stereo sound.

And then there was the iPhone.  And of course, everything had to change, and so did everything that came after (and this includes the Android phones).  A 3.5mm 4 pole jack:
T=left earpiece
R=right earpiece
R=ground
S=microphone
What?!?  With this configuration, old headsets will not work at all.  However, a 3.5mm 3 pole plug for music will work fine. 

Common to all headsets:  the microphones are all electret condenser type.  Sometimes the microphones in the headsets have a small amplifier circuit built-in, so the phone supplies a small voltage (~2 volts) to power this amplifier.  The bias voltage on the microphone circuit is also used to detect the insertion of the headset and switch the audio paths from the phone body to the headset.  If the phone measures ~100uA of bias current the audio paths are switched.

Specific Android/iPhone Interface Info

Audio Output (TX audio)
Output impedance > 20 ohms, AC-coupled
-20 dBV into 32 ohm load at "mid-volume" setting
Audio Input (RX audio)
Input impedance 2.2 kohm
DC-bias between 1.65 and 2.1 V
Detect connected device if bias current > 100 microamps
Input amplitude -45 dBV to -62 dBV (nominal)

Hardware Interface

Wolphi makes a "Wolphi-Link" interface that takes care of all the interface problems noted above.  It even includes TX-derived PTT control, sort of.  One end of the box accepts a 4-pole cable from your phone, and the other a 6-pin mini-DIN to go to your PACKET or DATA jack.  I do recommend the Wolphi-Link as the least painful approach.

However...

When I set it all up, the PTT wouldn't work on the TS-480.  After a fair amount of troubleshooting, I finally figured out that the idle PTT voltage coming from the DATA jack was very low, about 1.7 V.  In all my past interfacing experiences, the idle PTT voltage has been at least 5 V (or 8 V or 13.V).  Turns out it's really hard to electronically switch 1.7 V with generic devices.

The easiest solution was to completely disable the Wolphi-Link PTT by removing Q2 (the keying transistor).  Fortunately the TS-480 supports VOX from an input to the DATA jack, so the PTT solution was simply to activate DATA VOX.

One other very nice feature of the TS-480 is that both the input AF level and the output AF level to/from the DATA jack are front-panel adjustable.  That makes setting all the audio levels much easier.  The main thing:  NO ALC indication!!!