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Bluetooth protocols explained

Understanding the ABCs of Bluetooth in your car

Bluetooth® wireless technology is a natural for the car. Most people know that by "pairing" (connecting wirelessly, in other words) their Bluetooth phones with their car stereo receiver, they'll be able to engage in hands-free calling. But Bluetooth also has other functionality, like wireless streaming of music from smartphones and other Bluetooth devices to your car stereo.

Bluetooth in the car

It does all this by opening up a 2-way line of com­munication between your smartphone and your stereo, letting them have a conversation. You just need to make sure they can speak the same languages.

The easiest way to make sure your phone and stereo do the things you want — like playing music, answering calls, and supporting voice control — is to see if each one is compatible with certain specific Bluetooth protocols. And the easiest way to do that is to check your phone and stereo for the abbreviations we'll discuss below.

Add Bluetooth to your car with a new stereo

Whenever you're shopping for a Bluetooth stereo on our site, you'll find compatible protocols listed on the stereo's "Details" tab, under "Product Research". And remember: for a particular feature to work, both your phone and your stereo need to be compatible with the necessary protocol. So read up, decide what you want, and then get shopping for the car stereo that's right for you.

[Shop for car stereos with Bluetooth connectivity]

Bluetooth logo
Most Common Bluetooth Protocols
Protocol Abbreviation Benefit
Advanced Audio Distribution Protocol A2DP Audio streaming
Audio/Video Remote Control Protocol AVRCP Control over music playback directly from the stereo
Hands-free Profile HFP Hands-free calling through the stereo
Object Push Profile OPP Uploading of contact info to the stereo
Phone Book Access Profile PBAP Access to contact list from the stereo
Bluetooth makes hands-free calling possible

The Bluetooth Hands-free Profile means you can take a call without fumbling with your phone while you drive.

Get hands-free calling

Protocol: Hands-free Profile

Abbreviation: HFP

Most people get Bluetooth in the car for the Hands-Free Profile (HFP), which lets you make and take calls without having to touch your phone. HFP is the same protocol used by Bluetooth headsets for hands-free calling.

The advantage of having a car stereo that works with the hands-free profile is that incoming numbers show up on the stereo’s display, and you hear your callers over your car’s speakers.

When HFP is in action, Bluetooth designates your phone as a "gateway" and your stereo as a "hands-free unit". Your caller's voice passes through the phone and gets sent to your stereo, while your voice passes from an external microphone to your stereo, then to your phone, and on to your caller. Some Bluetooth stereos feature built-in microphones; others come with external microphones that you mount somewhere close to you, like on the sun visor or steering column, then plug into the back of the stereo.

Get access to your phone's contact list

Access your phone contacts through your receiver

Having your stereo access your contacts with the Phone Book Access Protocol makes it easier to place calls in the car.

Protocol: Object Push Profile or Phone Book Access Profile

Abbreviation: OPP, PBAP

Hands-free calling wouldn’t be quite as convenient if you had to use your phone to pull up your contacts. Fortunately, Bluetooth can help in two ways.

The first, and most basic, is with Object Push Profile (OPP). This protocol lets you upload your contacts from your phone to your stereo. How the process works varies by stereo and phone, but basically, you set up a push/pull relationship between your phone and your stereo; you ask your stereo to "pull" the contacts from the phone, while telling your phone to "push" the info to your stereo. Your stereo will also have a limit on the number of contacts you can upload.

The more advanced Phone Book Access Profile (PBAP) lets your stereo tap into your phone’s contacts instead of uploading them. The process typcially intiates itself automatically, and usually goes like this: once your stereo and phone are paired, your stereo will ask your phone, "hey, may I take a peek at your contacts?" Your phone will reply, "I'm not sure, let me check." You'll then get a message from your phone telling you that your stereo is asking to connect with its contact list. All you have to do is approve, and your contacts will show up on your receiver's screen. This makes placing calls much easier.

Many receivers will allow you to engage in voice dialing, but usually only if your phone allows voice dialing. There are a few receivers that will allow voice dialing just by being able to access your phone's contacts.

Enjoy wireless audio streaming

stream music using your bluetooth phone

The Advanced Audio Distribution Profile lets you stream suprisingly good-sounding audio to your compatible stereo.

Protocol: Advanced Audio Distribution Profile

Abbreviation: A2DP

Want to enjoy music from your phone with a pesky tangle of wires? Bluetooth audio streaming makes it happen. As long as your receiver and your phone "speak" Advanced Audio Distribution Profile (A2DP), they’ll make beautiful music together. It’s sure nice to play whatever you have stored on your device without actually having to plug it in. You’ll also be able to hear the audio from most of your smartphone’s music apps. And your backseat passengers can have some fun playing DJ by pairing their devices, too.

So why do they call this profile "Advanced"? It has to do with audio quality: A2DP plays higher-quality mono or stereo audio from formats like MP3 and AAC than standard, narrower Bluetooth audio.

Essentially, A2DP creates a "Source/Sink" relationship between your phone and your stereo, in which your phone, the source, sends signal to your stereo, the sink. A2DP is also used in products such as wireless headphones and wireless speaker systems.

[Shop for car stereos with Bluetooth connectivity]

Get control over music playback

bluetooth enabled receiver

With AVRCP, you get some control over wireless music playback (bottom). With version 1.3 of AVRCP, you get to see artist, album, and song info, too (top).

Protocol: Audio/Video Remote Control Profile

Abbreviation: AVRCP

The Audio/Video Remote Control Profile (AVRCP) allows control from your stereo over the music you’re playing from your phone or device, including songs from apps like Pandora® and Spotify. Bascially, AVRCP turns your stereo into a controller and your phone into a target. Much like a TV remote control, when you push a button on the stereo, AVRCP translates this action into a signal that it then sends to your phone. The end result: the ability to use your stereo's buttons or touchscreen to play, pause, and skip back and forth between tracks.

See song and artist info, too

Protocol: Audio/Video Remote Control Profile

Abbreviation: AVRCP

One of the neat things about connecting your iPod® or iPhone® to your stereo is that it’ll send "metadata" — song, artist, and album title info — to the display. In 2007, version 1.3 of AVRCP was launched, letting Bluetooth do it, too. So now, not only do you get control over your music, you get to see what's playing at all times, even when you're playing music from many popular apps. Newer versions of AVRCP even allow for browsing and manipulation of multiple players.

When it comes to audio playback, AVRCP epitomizes the 2-way communication Bluetooth establishes. Your phone, or other device, sends sound and info to the stereo, while the stereo sends commands to the phone. Sounds like a pretty harmonious relationship to us.

Sound clear?

We hope this article has given you a better understanding of how Bluetooth works. Knowing what to look for in phones and receivers will help you shop with confidence.

If you have any questions or just need a little help choosing the stereo that's right for you, contact one of our advisors.

[Shop for car stereos with Bluetooth connectivity]

  • Don Foley from Manchester

    Posted on 3/27/2023

    Thank you crutchfield

  • Donald Drach from Davenport

    Posted on 10/16/2022

    I have a sena in my helmet and an android phone. I want the three to work together seamlessly, is that possible with a system like this?

    Commenter image

    Dominic DeVito from Crutchfield

    on 10/17/2022

    Hi Donald - thanks for your question. We don't carry Sena products, so I can't speak to their capabilities. Luckily they offer support through their site, so a visit to should allow you to get in touch with them via email or web chat or support ticket request and hopefully someone there will be able to help you out!
  • Debbie Taylor from Collinsville

    Posted on 8/1/2022

    Help. I have the Deh-x8600bh in a car I just purchased. I have an android phone. My pairing for music via pandora is fine but I'm having trouble with the bt phone function. I get calls and can hear the caller but they can't hear me. How do I correct this?

    Commenter image

    Dominic DeVito from Crutchfield

    on 8/2/2022

    HI Debbie (again) - sorry to be replying to my own reply, but it just occurred to me that the problem might be with the Pioneer's external microphone. You may want to check that it is properly connected to the radio. If so, you may need to mount it in a different spot in the car so that your callers can hear you better. It's also possible that the microphone has failed as well. If so, one of our Advisors can advise you on a solution.
  • John jones from Atlanta

    Posted on 4/28/2022

    Where do I find my Bluetooth pin to connect to my stereo.

    Commenter image

    Dominic DeVito from Crutchfield

    on 4/29/2022

    John - the stereo owner's manual is always the best resource. If you don't have the manual and you bought your gear from Crutchfield, you can call Tech Support for free help setting up your gear. If you purchased your equipment elsewhere, I'd suggest a quick Google search. You shouldn't have any trouble locating the manual.
  • Bryan Parrish from bridgewater

    Posted on 11/26/2021

    Thank you for helpful information

  • Bryan Parrish from bridgewater

    Posted on 11/26/2021

    Thank you for helpful information

  • Angel Esparza from Rialto

    Posted on 5/16/2021

    how can I find the pin code to pair my phone though Bluetooth with a axm145bt Axxera ?

    Commenter image

    Ken Nail from Crutchfield

    on 5/17/2021

    Angel - the manual is always the best resource. If you don't have the manual and you bought your gear from Crutchfield, you can call Tech Support for free help setting up your gear. If you purchased your equipment elsewhere, I'd suggest a quick Google search. You shouldn't have any trouble locating the manual.
  • Adrian smith from Cedar Island

    Posted on 1/7/2021

    Hey i just bought a bv765blc radio and i forgot to check about navigation system will i be able to hook up google maps or something in that nature for navigation purposes and it show up on radio screen?

    Commenter image

    Ken Nail from Crutchfield

    on 1/8/2021

    Sorry to let you know, Adrian, that the BV765BLC doesn't support the display of navigation apps from your smartphone. If you have an iPhone, your best bet is to look for a receiver that supports Apple CarPlay. If you're an Android user, Android Auto is the ticket.
  • Helio from Arlington Tx

    Posted on 9/3/2019

    Bluetooth in stereo only works in park mode. Hos can I bypass?

    Commenter image

    Alexander H. from Crutchfield

    on 9/3/2019

    Helio, that shouldn't be the case. If you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.
  • juan san inocencio from Avon, MA

    Posted on 6/11/2019

    Thinking about replacing the radio on my 2014 Honda CRV with navigation system but not sure which radio to choose. Do I need a radio with or without navigation? or can I get a radio without navigation and use the navigation system that is already running in the car?

    Commenter image

    Alexander H. from Crutchfield

    on 6/11/2019

    Juan, you won't be able to retain factory navigation if you step up to a new receiver. So, you'll want to look at navigation receivers or those with Apple CarPlay/Android Auto if you're okay with using the nav apps on your phone. I've passed your question along to our Advisors for help. Someone will contact you soon to help you find the right receiver for your needs and vehicle.

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