TRRS and TRS Plugs and Sockets Explained

This tutorial will explain the differences between 3-pole (TRS) and 4-pole (TRRS) plugs and sockets.
If you’ve ever tried connecting a headset/microphone designed for one particular manufacturer’s phone to another and it didn’t work, it may be because the pinout was wrong.
I ran into this recently with the Movo PM10 Lavalier Microphone for iPhone and trying to use it with other devices, such as a camcorder, etc.
We sell the different parts to do your own prototyping and make your own custom cables/devices, however it doesn’t do much good if you don’t understand the pinout as it relates to your device.  So hopefully this article will help you better understand these pinouts.

For this article, I will be focusing on standard 3.5mm (1/8″) TRS and TRRS plugs and sockets.

What Does TRS/TRRS Mean?

Simply put, TRS means Tip Ring Sleeve (3-pole) and TRRS means Tip Ring Ring Sleeve (4-pole).

TRS (3-pole):

TRS is commonly used for stereo headphones, mono headsets, stereo microphones, auxiliary cables, etc.  The poles on these are usually straight forward, but it is possible they could vary.

TRRS (4-pole):

TRRS is commonly used for stereo headsets, such as cell phone headsets with an inline microphone, audio/video cables with stereo audio, etc.  The catch with the TRRS is the poles can vary between CTIA (newer) and OMTP (older) standards.  This applies to cell phones and different manufacturers.

 

TRS Pinout

For the TRS pinout, the pinout usually goes as follows:

  • Tip = Left Channel
  • Ring = Right Channel
  • Sleeve = Ground / Common

TRS Plug Pinout

TRRS Pinout

For the TRRS pinout, the primary difference is between the Mic and Ground/Common.
You can view the TRRS standards on Wikipedia for the different phone manufacturers and which standard they go by.

Since I mentioned the iPhone, they follow the CTIA Standard:

  • Tip = Left Channel
  • Ring = Right Channel
  • Ring = Ground / Common
  • Sleeve = Microphone

The OMTP Standard is as follows:

  • Tip = Left Channel
  • Ring = Right Channel
  • Ring = Microphone
  • Sleeve = Ground/Common

TRRS Plug Pinout

 

What Difference Do The TRRS Standards Make?

Let’s take the Movo PM10 microphone for example.  It is wired according to the CTIA Standard, therefore the sleeve is the Microphone (+) and the Ring is the Ground/Common (-).  The microphone inside is an electret microphone, which they have a positive and negative polarity.  They will NOT work in reverse.
So if you plug this microphone into an OMTP Standard device, the polarity will be reversed and it will not work.  In the case of a headphones with an inline microphone (such as the ones that come with an iPhone), the Left and Right channels will not have a ground connection and therefore will not work.  They will instead be connected to the microphone and that’s useless.

CTIA Standard vs OMTP Standard

 

What About TRRS to TRS Adapters?

Which standard TRRS to TRS (4-pole to 3-pole adapters) follow definitely matters.
Take our 3.5mm iPhone iPad Tablet Cell Phone Headset Adapter for example.  Since they’re made for iPhone/iOS devices, they follow the CTIA Standard.  This means the Ring instead of the Sleeve is the ground/common and this will match the Sleeve on the Microphone/Headphone ports as well.

 

Why Does My Microphone Still Not Work?

Let’s say you use a TRRS adapter on the Movo PM10 Lavalier Microphone and plug it into a camcorder and it still doesn’t work.  You may have the polarity correct, however it just doesn’t work.  So what’s the problem?
I ran into this when I tested it with my Canon Vixia camcorder.  The problem is the Canon Vixia camcorder doesn’t provide power to the microphone.  Electret microphones require a small voltage (usually around 1.8 – 3V DC) to work.  Most cell phones provide this voltage and will power the microphone just fine.  But in my case, the camcorder didn’t so I would have to build a circuit that would supply the missing voltage for the microphone to work.

Microphones such as the Audio-Technica ATR3350IS Lavalier Microphone uses a LR44 Button Cell battery to power it, so even if the device doesn’t provide power for the mic, it will work.

I’ll try adding a tutorial on how to build such a circuit soon.

 

What Next?

The next step is to start experimenting and trying it for yourself.  We’ve got a few items to help you get started:

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