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AUX Inputs: What Is the Auxiliary Input? What Is Its Use?


Comparison Table

Comparison Table


The Basics

What are AUX Inputs?

Auxiliary (AUX) inputs are simple audio connections that look like headphone sockets. Paired with an AUX-IN cable they will allow you to input sound from any media device with a normal headphone socket. They are one of the easiest ways to play music, audiobooks, or podcasts in your car. They can also transfer audio from navigation apps or phone calls. Many cars manufactured after 2007 have these fitted as standard.

What do AUX Inputs look like?

There are two types of AUX inputs in cars: 3.5mm and RCA. They are normally labeled ‘Line In’, ‘AUX-IN’, or ‘AUX’. In most cars, they are located on in the center console, armrest, or glovebox.

3.5mm AUX-Inputs

RCA AUX-Inputs

3.5mm AUX Inputs

3.5mm AUX-Inputs

RCA AUX Inputs

RCA AUX-Inputs

3.5mm AUX inputs are the most common type. They look like normal headphone sockets. Some cars (particularly Renaults, Peugeots and Citroens) have RCA AUX inputs. These consist of two inputs, each slightly larger than headphone sockets with colored plastic rings around (normally one white, one red).

How do I connect to them?

To use these inputs you will need a 3.5mm-3.5mm or 3.5mm-RCA AUX-IN audio cable. This cable will go between the headphone socket on your media player and your AUX input. You can get these cables from any good electronics shop. We sell our own InCarCables range on They have an excellent reputation and won’t break the bank!


i. Plug one end of your AUX-IN cable into the headphone socket of your media player. ii. Plug the other end of the cable into your car AUX-IN socket. (For an RCA AUX input plug in the double RCA end of the cable.)
iii. Place your car stereo into AUX mode. (Normally there is an AUX or source button on the radio). iv. Click play on your media player. Then turn up the volume on your media player to around 75%. Finally, adjust your stereo volume as necessary.


Will it work with my iPod, iPhone, iPad, smartphone, mp3 player, or tablet?

Standard AUX cables will connect to any media device with a normal 3.5mm headphone socket (which is fitted to nearly every modern media player).

Will it work with my car?

To use this method your car must have an AUX input fitted. Many modern cars have these fitted as standard. They are normally located in your car’s center console, armrest, or glovebox.


Which of my devices’ features can I use?

AUX inputs can only transfer audio from your media device to your car. This means you will be able to play music, audiobooks, or podcasts through your car’s speakers. You can also transfer the audio from phone calls and other applications such as Google Maps™ or Spotify.

Will I be able to see information from my device on my car display?

No. AUX inputs can only transfer audio signals. They won’t be able to transfer song titles to your car’s display when playing music or show maps from your navigation app.

As a result, when using AUX inputs, it may be helpful to still be able to see your phone display (hands-free). Car mounts such as Kenu’s portable car mount can help by safely placing your phone in your line of vision on the dashboard. If you use a mount please take care to not allow your device to distract your attention whilst driving.

What if I want to make phone calls?

The most common way to make phone calls in modern cars is hands-free through Bluetooth®.

There is nothing to stop you using AUX inputs for phone calls. If you make or answer a call whilst your phone is connected to the input, the audio from that call will be played through the car’s speakers. The phone will then pick up your voice from its inbuilt microphone (which will normally be on a more sensitive setting if the AUX cable is plugged into the phone). You need to be careful not to turn up the volume on the car speakers too much, however, as you may get echo/feedback effects from your phone microphone picking up the caller’s voice being played over the speakers!

Please remember it is illegal in the UK to use a hand-held mobile phone when driving. Again a mount can help you to use your phone hands-free but do not allow your device to distract your attention whilst driving.

Another option is to add Bluetooth functionality via your AUX input, via devices like Belkin’s In-Car Audio Connect. This device plugs into your AUX input and 12V socket and then connects to your phone wirelessly via Bluetooth (so your phone can stay in your pocket). It comes with a control button, allowing you to listen (and control your music) or make hands-free calls.

What about navigation?

Many modern smartphones have built in navigation (or navigation apps from third parties such as TomTom). If your phone is connected to your AUX input then the audio from these apps when in use will be played through your car speakers. You can use a mount so you can see the map in your line of vision.

Will I be able to select the music being played using my car’s controls?

No. With AUX-inputs you will need to select the music being played on the device itself. This may be preferable if a passenger is selecting songs to play. Alternatively, you can always set up playlists before you set off. You will however still be able to alter the volume using your car controls.

If you want to control via your car you will need to use a different connection method like a USB inputBluetoothMedia inputs, or Car Mobile Operating Systems.

Will it charge my mp3 player/smartphone?

No, AUX inputs are designed to input analog audio signals to your stereo so they can’t charge your device. However because AUX-IN cables connect to the headphone socket of your phone, they generally leave the charging port on your device free. This means there is nothing to stop you from charging your device simultaneously. You will need a charging cable and either a USB port or 12V-USB charger. There are lots of options to choose from.

What about sound quality?

AUX inputs provide a direct audio line into your stereo so the sound quality is normally pretty good. However, AUX inputs, like headphones only accept analog audio signals. This means the conversion of your music files from digital to analog is done by your music player/ smartphone. Given smartphones are portable, battery-powered devices they are not always the best at doing this. You can read more about sound quality here.


AUX inputs are a simple way to play music in your car from pretty much any device. They are close to universally compatible, so if your car has an input you can pick up a cable and get started! InCarCables sell a brilliant range if you need one!

They do have some limitations, however, particularly given that they can only transfer audio signals and will not integrate with your car controls. As a result, it is always worth considering other connection options if they are available in your car.




  • Fitted to most modern cars.
  • Simple and easy to use.
  • Universally compatible – will work with any media player with a standard (3.5mm) headphone socket.
  • Control is via your media player, making it easy for passengers to select songs.
  • Can transfer audio from phone calls and other applications such as Google Maps or Spotify.
  • May not be fitted to older car models.
  • Will not integrate with car controls.
  • Will not transfer information to the car display.
  • Will not charge your device (but leaves charging socket free).
  • AUX sockets and cables can wear and sometimes will need repairing or replacing.




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