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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > iPhone, iPad & iPod > iPhone headphones: how does the mic work?

iPhone headphones: how does the mic work?
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badtz
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Aug 2, 2007, 01:13 AM
 
I guess this could apply to all headset/mic combos but ....

How is the iPhone headset picking up the microphone information and sending it to the iPhone?

How is the audio information [technically] transmitted to the iPhone? Does that mean that iPhone has some sort of chip to process information in the reverse? Does that mean the headphone port could hypothetically be used as a microphone port also [like the iPods]?

Thanks for any help
     
stevesnj
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Aug 2, 2007, 10:15 AM
 
its all done thru the wire
MacBook Pro 15" i7 ~ Snow Leopard ~ iPhone 4 - 16Gb
     
Earth Mk. II
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Aug 2, 2007, 10:32 AM
 
There's a second ring on the connector that carries the microphone signal.

Most headphone jacks use Tip-Ring-Sleeve (TRS) connectors, but headphones with a microphone typically use Tip-Ring-Ring-Sleeve (TRRS).

TRS connector - Wikipedia, the free encyclopedia
/Earth\ Mk\.\ I{2}/
     
badtz  (op)
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Aug 2, 2007, 01:32 PM
 
Originally Posted by Earth Mk. II View Post
There's a second ring on the connector that carries the microphone signal.

Most headphone jacks use Tip-Ring-Sleeve (TRS) connectors, but headphones with a microphone typically use Tip-Ring-Ring-Sleeve (TRRS).

TRS connector - Wikipedia, the free encyclopedia
Great answer, that's exactly what I was looking for

An aside: does that mean the chip that processes the microphone (from the headset) input is the same that processes the microphone input from the phone itself?

     
Earth Mk. II
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Aug 2, 2007, 02:03 PM
 
No idea.

If I had to guess, I'd say it's likely, but I haven't seen any iPhone tear-downs that point to its DAC or ADC (probably because they're not of great interest to the hacker communities). It's also possible that those functions are handled by either the iPhone's application processor or the baseband.

In general terms, there is some device that converts the analog microphone signal into a digital signal, which is then compressed and encoded before being transmitted to the cell tower. When receiving, its the same process; but in reverse, then it's sent to an amplifier and then into the earpeice/headset/loudspeaker.

I have no idea how this process is implemented in the iPhone, or if the microphone input is even accessible to other applications. I suspect that it is - but that's 100% conjecture.
/Earth\ Mk\.\ I{2}/
     
   
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