The iPhone, Apple has said numerous times, is three products in one: a cell phone, an Internet device, and Apple’s best ever iPod. Except, as users are finding, it’s not exactly an iPod. Try to use it with one of the over three thousand iPod accessories out there and you’ll probably be surprised by the results: you can’t upgrade it with a larger video display, use it in the car with many recent FM transmitters, or fully enjoy its multi-functionality while it’s connected to most iPod speakers. Here’s what we’ve discovered so far.


Important Initial Tip: If you’re having problems with the audio output from your iPhone, make sure that you’re properly using iTunes’ and iPhone’s Sound Check features. Buried in iTunes’ Preferences under Playback, this odd but useful iTunes feature can be activated to figure out the proper volume levels for all of the songs in your iTunes library, so that music coming out of your speakers stays at a consistent volume without huge spikes or valleys. If it’s not activated, iTunes may not have the Sound Check volume levels for the songs in your library.
As with iPods, iTunes sends any Sound Check data it collects for your songs to iPhone. In the past, this data sat on iPods unused unless you similarly activated the Sound Check feature in their settings menus. Now, unlike iPods, iPhone comes with Sound Check turned on, which is a problem if iTunes doesn’t have stored data. Consequently, iPhone output to accessories can vary wildly in volume, and appear to be capped at a level much lower than the iPod’s. If you’re experiencing major volume problems with your iPhone and accessories, turn Sound Check off until you’re sure iTunes has collected all the data to make it work properly.
What happens when iPhone is connected to common Apple-made iPod accessories?
Nike+iPod Sport Kit: Does not work at all. iPhone displays “This accessory is not supported by iPhone.” message.

iPod Camera Connector: Same as above.

iPod Radio Remote: Same as above, except that it occasionally displays another message.
Notice anything about all three of these accessories? They all have the word “iPod” in their names. None works with the iPhone.
But the reasons are different from accessory to accessory. The iPod Camera Connector historically treated iPods as mass storage devices for transfers of digital cameras’ pictures, but iPhone doesn’t operate as a mass storage device, and lacks “Disk Mode” for storing files like a hard disk. For this reason, devices accustomed to reading or writing to an iPod’s database without iTunes just won’t work. Sorry, iLoad. By contrast, Apple could and might add support for the Radio Remote, and while it could do the same for the Nike+iPod Sport Kit, it could also just release an updated Sensor compatible with iPhone’s existing wireless hardware. Whether or not this happens is up to Apple, but we’re not holding our breath—if full-sized iPods aren’t Nike+ ready, why would iPhone be?
What happens when iPhone is connected to certain common third-party iPod car accessories?

Belkin TuneFM: Does not appear to work at all as an FM transmitter. Displays “This accessory is not made to work with iPhone” screen. User is asked, “Would you like to turn on Airplane Mode to reduce audio interference (you will not be able to make or receive calls)?” and given a yes or no option. Pressing any TuneFM button calls up “iPod accessory attached” screen.
DLO TuneStik: Displays those warnings. Allows remote control of simple iPod features. No tuning for FM transmitter. Pressing transmitter button calls up “iPod accessory attached” screen.

iTrip with Dock Connector: Displays those warnings. Sometimes works as an FM transmitter to play iPod audio through radio.
XtremeMac AirPlay Boost: Displays those warnings. On-screen radio tuning for FM transmitter does not work at all. Tuner remains set to whatever channel you last set with an iPod.
Does broadcast properly to that station on previous settings unless you hit buttons.
XtremeMac RoadShow: Combines a Dock Connector-based car charger with audio and video outputs. Displays warnings; iPhone charges but does not perform audio or video.
Old FM transmitters may or may not work with iPhone. It doesn’t allow accessories to fill up its screen with text, even on a “Do Not Disconnect” screen, so any accessory that used that method for tuning no longer works fully, or in some cases, at all. Remote controls may work for simple iPod features, but if they have other features, they may not.
What happens when iPhone is connected to iPod Voice Recorders?
iPhone does not support iPod Voice Recorders such as Belkin’s TuneTalk Stereo, Griffin’s iTalk Pro, or XtremeMac’s MicroMemo, and does not appear to have any ability to store voice recordings, except for its essentially unrelated Visual Voicemail feature.

What happens when iPhone is connected to certain iPod speakers?
We’d heard rumblings back in January that TDMA noise—the sound emitted by cell phones when they communicate back and forth with towers—was going to make iPod-ready speakers less than iPhone-ready. Our initial testing bears this out: unless it’s in Airplane Mode, iPhone puts out loud TDMA noise no matter which speakers it’s around (computer speakers, iPod speakers, and so on), and if the speakers aren’t well-shielded, you’ll hear the noise. Apple offers you the choice to turn on Airplane Mode every time you connect iPhone to an accessory, and sometimes keeps nagging you with it over and over, depending on how the accessory “talks” with iPhone.
Bose SoundDock: iPhone charges and speakers work, but with mild TDMA noise unless Airplane Mode’s on. Nag screen came up multiple times during one test.
Altec Lansing iM7: Dock does not close. iPhone charges and speakers work, but with loud TDMA noise unless Airplane Mode’s on. Nag screen came up once during test.
Apple iPod Hi-Fi: Nag screen appears, but speakers work.
Macally TunePro: iPhone charges, but speakers do not work, even if Airplane Mode’s on. Moderate TDMA noise.