What's Up with Those 3.5mm Plugs?

3.5mm Plugs

Dear Dr. Headphone,

I have recently bought a new headphone with mic from an Apple Premium Reseller, however when I connect it to my old Sony Ericsson phone, the microphone doesn’t work. Speakers work fine. Also, I’ve tried to connect it to my laptop, the microphone doesn’t work either. I was going to return it to the shop, but my girlfriend tried it on her iPhone and it works fine. What do you think is the cause, are my phone and laptop broken?


Hi, Ryan. The chance of both your phone and laptop having a microphone problem is slim, although it is possible.

However, I think it’s more likely related to a compatibility issue between your headphone and devices. You see, there are a few types of 3.5mm connectors in the market, some have different number of poles and some have different alignment of poles.

In terms of number of poles, there are 3 types of 3.5mm plugs. (a) 2-Poles are for mono audio, (b) 3-Poles are for stereo audio and (c) 4-Poles are for stereo audio with microphone, also known as TRRS.

All headphones with microphone have 4 poles, but the pin-alignment (order or the connection pin) can be different. There are two main standard, OMTP and CTIA.

The difference between the two is the or-der of the last two pin, OMTP has its micro-phone at pin 3, CTIA has it at pin 4.

Unfortunately, there are no identification on packaging with regarding to which system a device or accessory is using. But with the adoption of CTIA by Apple, Samsung (newer models), HTC, Microsoft’s Lumia, OMTP is slowly being phased out.

The same applies to laptops with single 3.5mm jack, some brands use OMTP, while others have adopted CTIA.

I recommend you consider upgrading to a new smartphone, most will be CTIA com-patible. As for your laptop, you can consider buying an Accutone 3.5mm-to-USB adapter, which supports CTIA. This accessory will turn your headphone into a USB headset.

(Top Image Credit: Dave Crosby)

3.5mm connectors alignment

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