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](http://images.crutchfieldonline.com/ImageBank/v20150319120800/ImageHandler/scale/978/978/core/learn/article/2874/bt car.jpg)
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](http://images.crutchfieldonline.com/ImageBank/v20120726145900/ImageHandler/scale/323/323/ca/learningcenter/articles/2874/Logo-Bluetooth.jpg)
Most Common Bluetooth Protocols | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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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](http://images.crutchfieldonline.com/ImageBank/v20171020084800/ImageHandler/scale/978/978/core/learn/article/2874/bluetooth-call.jpg)
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](http://images.crutchfieldonline.com/ImageHandler/scale/489/489/products/2012/27/113/h113DDX419-o_phonebook-1.jpeg)
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](http://images.crutchfieldonline.com/ImageBank/v20120725164400/ImageHandler/scale/489/489/ca/learningcenter/articles/2874/h113DDX419-o-phone-2.jpg)
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](http://images.crutchfieldonline.com/ImageHandler/scale/489/489/products/2012/group/h113DDX419-o_music.jpeg)
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.
Comments (58)
Please share your thoughts below.
Jake from Phoenix
Posted on 11/25/2023
When Bluetooth is activated on my iPhone, am I able to adjust the volume of the music being played? Also, is there a wired remote that is used with the stereo? My location will be unavailable to use the IR type remote since there is no line of sight.
Dominic DeVito from Crutchfield
on 11/27/2023
Brian Hatt from Greenville
Posted on 10/25/2023
My girlfriend and I share the truck and curious how you cycle through the source between my iPhone and her android on the JVC KX-850bts? Is there an "EASIER" way? Thank you
Dominic DeVito from Crutchfield
on 10/26/2023
Ray
Posted on 8/17/2023
How does the bluetooth version come into play eg. Bluetooth 4.2 vs Bluetooth 5.0
Dominic DeVito from Crutchfield
on 8/18/2023
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?
Dominic DeVito from Crutchfield
on 10/17/2022
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?
Dominic DeVito from Crutchfield
on 8/2/2022
John jones from Atlanta
Posted on 4/28/2022
Where do I find my Bluetooth pin to connect to my stereo.
Dominic DeVito from Crutchfield
on 4/29/2022
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 ?
Ken Nail from Crutchfield
on 5/17/2021