Will your current accessories work with iPhone 4?

We’ve been taking your iPhone 4 questions, answering them in a series of articles. But among the most common questions have been ones about whether or not accessories that work with previous iPhone—or iPod—models will work with Apple's latest phone.

Given that new iPhone and iPod models have, in the past, included circuitry changes that that rendered existing accessories obsolete, as well as the fact that the iPhone 4's physical design is very different from that of its predecessors, these are valid concerns. As we do with every new iPhone, iPod, and iPad, here’s a quick rundown of which accessories work—and which don’t.

Belkin's Shield Eclipse

Cases: As should be obvious, given the completely new design of the iPhone 4, cases for existing iPhones won’t fit—compared to the iPhone 3GS, the iPhone 4 is thinner in the middle, less-rounded at the edges, and narrower overall. However, I mention cases here for the same reason I mentioned them when I talked about the iPad and accessory compatibility: Some vendors started producing iPhone 4 cases before the phone was actually released, and based on some of the early case samples we’ve seen, not every early case is as usable as it could be. Most of the early samples we’ve seen fit the iPhone 4’s dimensions, but on some, the phone’s buttons and switches are difficult to operate, and on others, the case doesn’t provide a large-enough opening for the camera(s) and flash. When buying a case for your new iPhone, I recommend trying the case first—or at least buying from a store with a good return policy.

Another popular protection option for iPhones is a protective film for the screen, or for the entire body of the phone, from companies such as InvisibleShield and BodyGuardz. If our experiences with the iPhone 3GS’s screen are any indication, the iPhone 4’s screen should be nearly impervious to scratches—I used my iPhone 3GS for a year with the screen unprotected and still don’t have a scratch on it. If you just can’t stop worrying about screen scratches, Power Support has long made my favorite screen films.

If the glass back of the iPhone 4 is made of the same grade of glass as the phone’s screen, you may be able to avoid covering it with a case, as well; however, we’ve read claims that the iPhone 4’s screen and backside use different grades of glass. In either case, if you find yourself affected by the iPhone 4’s reception issue, where holding the phone a particular way essentially reduces reception by bridging two of its external antennas, a case seems to ameliorate the problem by preventing you from touching those antennas. (Apple’s yes-it-really-does-cost-$29 iPhone Bumper, which is simply a rubber-and-plastic edge guard, also seems to help in this respect.)

Bowers & Wilkins' P5

Headphones and wired headsets: The iPhone 4 features the same multi-function headphone jack as the past few iPhones and iPod touch models. It works with standard stereo headphones with a 1/8-inch (3.5mm) stereo miniplug, as well as stereo headsets—from Apple and third-party vendors—that include an inline remote control and microphone. (The iPhone 4 includes Apple’s three-button—play/pause, volume up, and volume down—earbuds with microphone.) When using the iPod app, the inline play/pause button works just as it does with many recent Apple products: a single press toggles playback, a double-press skips forward, a triple-press skips backward, and a press-hold activates the iPhone’s Voice Control feature. When using the Phone app with a wired headset, the iPhone’s microphone and speaker are disabled in favor of the microphone and earpieces on the headset, and the inline play/pause button performs phone-related functions.

The microphone on a wired headset should also work in any app that allows audio recording, including the stock Voice Memos app. It also works with the video mode of Apple’s Camera app; in fact, the inline play/pause button acts as a record/pause button.

Microphones: As I just noted, the inline microphone on any iPhone- or iPod-compatible headphones or headset works as a mono microphone for recording audio (from within an app that supports recording, of course). These microphones also work in Skype and similar apps.

On the other hand, dock-connector microphones, such as Blue’s Mikey, don’t work at all. According to a post on the Audiofile Engineering forums—the company makes the Fire field-recording app—Apple has changed the audio-input circuitry on the iPad and iPhone 4; microphones and other audio-input accessories must now convert audio to a USB-audio signal before sending that signal to the iPhone’s dock-connector port. (Older iPhones and iPods accepted analog audio input, but that circuitry has been removed.)

Unfortunately, unlike with the iPad, you can’t connect a USB microphone or headset to the iPhone using the iPad Camera Connection Kit. The Camera Connection Kit doesn’t work at all with the iPhone. Similarly, as with previous iPhones and the iPad, the microphone on Bluetooth headphones or headsets, which can be used for phone calls, doesn’t work for general audio recording.

Plantronics' Voyager Pro

Bluetooth mono headsets: The iPhone 4 lets you use any standard mono Bluetooth earpiece or headset for making and taking phone calls. With most recent headsets, you can use standard single-button controls: press to answer or end a call, double-press to redial the last number, and press-hold to activate Voice Control. If you have an A2DP-compatible headset or earpiece, you may also be able to listen to non-phone audio—in mono, of course.

Bluetooth stereo headphones and speakers: As with the previous two generations of iPhone and iPod touch models, the iPhone 4 lets you use Bluetooth stereo headphones and speakers to listen to the phone’s audio output. In my testing with a number of stereo-Bluetooth accessories—headphones, speakers, and Belkin’s Bluetooth Music Receiver—pairing was quick and easy, and most audio was routed through the headphones or speakers. However, as with the iPad, audio from the Skype app wasn’t routed through the Bluetooth headphones or speakers. Similarly, on Bluetooth headphones or speakers that include a microphone for phone conversations, that microphone didn’t work in apps other than the Phone app.

One issue I experience, when listening to music at the gym through either of two different Bluetooth headphones, was choppy audio streaming. I’ve thus far tried deleting all Bluetooth device pairings and re-pairing just one or the other set of headphones, but I haven’t been able to eliminate the stutters and dropouts.

The iPhone 4 also continues to suffer the same Bluetooth limitation as previous Apple devices by not fully supporting AVRCP (the Audio/Video Remote Control Profile), which is the Bluetooth feature that lets you control playback using buttons on your Bluetooth headphones or speakers. Whereas a good number of Bluetooth audio accessories include buttons for skipping tracks, and some even let you browse your device’s menus, the iPhone 4 still supports only the most-basic AVRCP functions: play/pause and stop. I was hoping iOS 4 or the iPhone 4 would finally include this fairly basic functionality, but it’s still missing. It looks like I’ll have to continue to use the Bluetooth Helper app to control playback at the gym without having to take my iPhone out of my pocket.

One change iOS 4 did bring—to both the iPhone 4 and previous iPhone and iPod touch models—is the ability to control Bluetooth playback volume using the iPhone’s own controls. (You were previously limited to adjusting the volume level using your Bluetooth headphones or speaker system’s own volume controls.) This change does mean that you now have to perform some level matching to find the iPhone volume level that gives you the best range of volume on your Bluetooth headphones or speakers, but it’s a welcome tradeoff. For example, last year I tested a set of Bluetooth headphones that I couldn’t use because the headphones’ lowest volume level was still too loud. I can now reduce the iPhone’s volume level and use those headphones comfortably.

Charging/power accessories: If the iPad’s charging challenges had you fretting about using your existing power accessories with the iPhone 4, rest easy. The iPhone 4 has the same—or at least similar-enough—charging circuitry as the iPhone 3GS and recent iPod touch models. Which means that any dock-connector charger or external battery that uses USB power should work fine with the iPhone 4. (You may recall the brouhaha a few years back when Apple switched to USB power for iPhone and iPod charging, rendering useless those older chargers that sent power over FireWire pins. At this point, I think few people are still trying to use such older accessories, but I note this limitation here in the name of thoroughness.)

Altec Lansing's inMotion Classic

Docking speakers: “Speaker docks”—those audio systems that include a convenient dock cradle for your iPhone or iPod and that grab audio (and possibly video) while simultaneously charging the device—are among the most popular iPhone accessories. They’re also among the most expensive, so they generate the most concern about compatibility when Apple releases new iPhones. The good news here is that if your docking speaker system worked with the iPhone 3G or 3GS, it should work fine with the iPhone 4; if the system includes playback controls, those controls should work as expected with the iPhone 4.

Of course, as with previous iPhone models, if your docking speaker system doesn’t sport the official Works With iPhone designation, there’s a chance you could hear interference when your phone accesses the cellular network. For example, when you receive a call or when Mail checks for new e-mail, you could hear noise through the speakers. Connecting your iPhone 4 to a non-certified speaker system will usually prompt a warning message on the iPhone’s screen, along with an offer to put the phone into Airplane Mode to avoid such interference. And, as with power accessories, if you’ve got an older iPod dock that charges using the dock-connector port’s FireWire circuitry, that dock won’t charge your iPhone 4 without an adapter such as CableJive’s Charge Converter.

If your system includes a dock cradle that uses Apple’s Universal Dock design, note that Apple doesn’t include with the iPhone 4 the necessary dock insert for the phone to fit securely in the dock. As with other recent iPhone models, you’ll need to purchase this dock adapter separately: Apple sells a 3-pack for $9. It’s a shame Apple doesn’t just include an adapter with the iPhone.

Powered speakers and standard stereo systems: As with any audio device, you can connect your iPhone 4 to a set of powered speakers or to your home stereo system using standard audio cables. The drawback, of course, is that you lose any on-speaker controls that require a dock connection, as well as the capability to charge your iPhone while listening. You’ll get the best sound quality by grabbing a line-level audio signal from the iPhone—for example, by using the audio-out jack on Apple’s iPhone 4 Dock or Universal Dock (with the above-mentioned dock adapter), or using one of SendStation’s PocketDock adapters.

FM transmitters: If your only option for getting audio into, say, your car’s stereo is an FM transmitter, you’ll get essentially the same results with the iPhone 4 as with previous iPhone models. Which is to say that performance will vary widely depending on your location, the saturation of the airwaves around you, your car’s stereo, and seemingly myriad other factors. In testing dock-connector-based FM transmitters, my colleague Christopher Breen found that such accessories successfully grabbed audio from the iPhone’s dock-connector port and, if the transmitter included USB-charging capabilities, charged the iPhone 4. If you have a simpler FM transmitter that just plugs into the iPhone’s headphone jack, it will also work, although it obviously won’t be able to charge the phone.

If an FM transmitter isn’t Works-With-iPhone certified—and, truthfully, even if it is—you may experience interference from the phone’s wireless activity.

Video-out accessories: The iPhone 4 appears to use video-output circuitry similar to that of the iPad. Which means that as long as you have a recent, Apple-certified video accessory—for example, Apple’s Composite AV or Component AV cables, Apple’s iPad Dock Connector to VGA Adapter, or compatible third-party cables and docks—you’ll be able to watch your iPhone 4’s video on a TV, projector, or other external video device. (A couple years back, Apple changed the video circuitry in the dock-connector port, so older video-out accessories won’t work with recent iPhones and iPods.)

Apple's Component AV Cable

However, as with the iPad, there are some significant limitations here. The biggest is that you can’t project everything you might see your iPhone’s screen—only particular apps provide video output, and that list of apps is fairly short: the video mode of the iPod app, the slideshow mode of the Photos app, some video content displayed in Safari, and the YouTube app. (Apple’s support document about video output also lists the Keynote app, which is currently available only for the iPad.) I assume that, as with the iPad, developers will be able to take advantage of this feature—for example, with the iPhone version of the Netflix app—but for now your choices are limited.

The other limitations relate to copy protection and video-output resolution. When using the iPad Dock Connector To VGA Adapter, video output from the iPhone 4 is 1024 by 768 pixels with a 720p scan rate. However, because VGA doesn’t support High-bandwidth Digital Content Protection (HDCP), you can’t watch iTunes-purchased HD videos using the VGA Adapter. The alternative is to either sync the non-HD versions of movies (using the option in iTunes to do so) to your iPhone, or use Apple’s Composite or Component AV Cable. However, even the latter option is crippled, as HD videos are reduced to 480i (for the Composite cable) or 480p (for the Component cable) when output to a TV. As Jason Snell noted in our iPhone 4 review, it’s a shame that a device that can handle HD video can’t display that video on a TV.

Camera connectors: Unfortunately, neither of Apple’s accessories for transferring photos from your digital camera or memory card—the iPad Camera Connection Kit nor the older Camera Connector for iPods—works with the iPhone 4. Similarly, you can’t use the iPad Camera Connection Kit to connect other USB devices.

Interestingly, you can use the iPad Camera Connection Kit in the other direction—to transfer photos or movies from your iPhone 4 to your iPad.

Apple's Bluetooth Wireless Keyboard

Keyboards: Wait, what? Yes, keyboards: The iPhone 4 has inherited the iPad’s capability to connect to an external keyboard—specifically, a Bluetooth keyboard or, with the right adapter, the iPad Keyboard Dock—for lengthy typing sessions. Check out our article on using keyboards with the iPad for more details, but the gist is that any standard Bluetooth keyboard should be able to pair with the iPhone and make marathon typing sessions easier. You can use the keyboard’s arrow keys for navigating documents and selecting text, and when using a Mac-compatible keyboard, you can even take advantage of editing shortcuts such as Command+C (copy), Command+X (cut), Command+V (paste), Command+Z (undo), and Shift+Command+Z (redo), as well as Option-key shortcuts for typing diacritical characters. (Some Cocoa/emacs editing shortcuts—for example, Control+A, Control+E, and Control+K—also work.)

Apple’s Wireless Keyboard offers additional benefits. Besides being impressively thin and portable, Apple’s keyboard sports brightness, playback, and volume controls that work with the iPhone.

Other accessories: We obviously haven’t been able to test every accessory out there, so there may be products that worked fine with the iPhone 3GS but don’t work with the iPhone 4, and there may be accessories that are electrically and electronically compatible but that don’t fit physically. For example, several Macworld readers have told us that TomTom’s iPhone Car Kit doesn’t work with the iPhone 4: at least one person reports that the iPhone 4 doesn’t fit in the Car Kit’s cradle, while another claims it does fit but that the iPhone doesn’t recognize the Car Kit’s circuitry.

Overall, however, it appears that most accessories that worked with the iPhone 3GS should work fine with the iPhone 4. If you have any other accessory-compatibility questions, let us know in the comments. We’ll of course be covering iPhone 4 accessories in the coming weeks and months, so stay tuned.

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