[maemo-developers] N800 audio connector jack

[From: Jami Pekkanen]

Jami Pekkanen wrote:
> Continuing my monolog.
> 
> I came to think to me that this could be done with a diode.
> Unfortunately my knowledge in them is even worse than with resistors.

I took some lessons from Wikipedia and came up with a circuit diagram 
that could give similar resistances than the headset:

      --- R1 -----
+   |            |
  ----- V1 -- R2 ----
                     |-
                     M
                     |+
  -------------------
-

Where R1 is 1.8 kOhm resistor, R2 is 2.7 kOhm resistor, V1 is a diode 
and M is the plugged in microphone. The diagram may be wrong way around, 
but the idea is that to one way the circuit has ~1.8 kOhm resistance and 
to another ~1.1 kOhms. However, at least my diode (1N4004) seems to have 
too high set-on voltage for my multimeter's ohmmeter while the headset 
can be measured OK, so I can't verify the results with it.

Also I noticed that there seems to be two inductors, one semiconductor 
and a small resistor (50 Ohm) in the headset and there's probably a 
bigger resistor in the push-button. There also was some component 
between the microphone's pins which I assume is a conductor for the mic 
(I lost the component). Also I can't get any readings of the 
semiconductor (it's marked V01, which would say it is one) and I have no 
idea how to measure specs of the inductors. However, I'd guess that the 
circuit has some kind of transformer for the microphone, which could 
also lower the set-on voltage of the diode.

So to put the above together, I have mostly faint guesses how the system 
may work and any advice from people with more knowledge in electronics 
would be very appreciated.

PS. This seems to drift quite a bit away from the list's topic, so feel 
free to tell me to shut up when you get enough of these ramblings ;)

- Jami