[Gta04-owner] Headset jack adapter

NeilBrown neilb at suse.de
Mon Sep 24 01:15:43 CEST 2012

On Sun, 23 Sep 2012 23:24:45 +0200 Gilles Filippini
<gilles.filippini at free.fr> wrote:

> Hi,
> Dr. H. Nikolaus Schaller a écrit , Le 22/09/2012 15:30:
> > can it be that Nokia has different standards?
> > 
> > We have experimented and tested the GTA04 design with this one:
> > 
> > http://www.google.com/search?client=safari&rls=en&q=nokia+ad52&ie=UTF-8&oe=UTF-8
> > 
> > And the pin assignment is described in the manual in section 6.10.
> > It is based on the idea that you can also use a 2 wire 3.5mm headset w/o microphone and a AV chinch adapter cable for TV-out.
> >From what I understand using a multimeter, the AD-56 I bought has
> microphone and shield inverted from the GTA04 pin assignment. Shield is
> on pin 1 (inner end) and microphone on pin 2.
> I'll try to invert them, but I'll need luck; the wires are so thin :/

That is what I had as well.  I thought it might by why the headset was so
cheap, but maybe not.

Quoting from  http://en.wikipedia.org/wiki/TRS_connector

Mobile phones

   Several mobile phones, particularly smartphones, feature 3.5 mm TRRS connectors to facilitate
   attaching headphones/hands-free kits. 2 different forms are frequently found, both of which
   place left audio on the tip and right audio on the first ring (mirroring the configuration
   found on stereo connectors). Where they differ is in the placement of the microphone and return
   contacts. The first, which places the return signal on the second ring and the microphone on
   the sleeve, is used by Apple's iPhone line, HTC devices, latest Samsung's, Nokia and Sony
   phones, among others. The second, which reverses these contacts, is used by other Samsung
   smartphones and some Sony Ericsson phones.[22]

The GTA04 places 'return' on the second ring (counting from the Tip) and the
'microphone' on the sleeve.  So it should be compatible, though that does
mention 3.5mm, not 2.5mm

However earlier it says:

   A three- or four-conductor version of the 2.5 mm plug is widely used on
   cell phone handsfree headsets, providing mono (three conductor) or stereo 
   (four conductor) sound and a microphone input. Common stereo headphones with
   the 2.5 mm plug are often not compatible with this type of socket. A 3.5 mm
   version of this plug is now commonly available on mobile telephones as well.
   A 3.5 mm stereo-plus-mic jack is available that is compatible with standard
   3.5 mm stereo headphones, e.g. Nokia has been widely using TRRS connectors with
   3.5 mm diameter since 2006. The selected pin assignment, with ground on the sleeve,
   is as well standardized in OMTP[7] and has been accepted as a national Chinese standard
   YDT 1885-2009.

This seems to say that Nokia selected a pin assignment with ground on the
sleeve ... which is what we are finding, but is different from what it says
in the section on "Mobile phones".

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