On April 6, AT&T revealed that it would allow owners of old, off-contract iPhones to unlock them starting April 8. AT&T has kept old iPhones locked to its network since the original iPhone launched in 2007, so this is a huge change in stance for the carrier. Before April 8, the only way to unlock an iPhone from AT&T's network was to jailbreak it.

AT&T explained, "The only requirements are that a customer's account must be in good standing, their device cannot be associated with a current and active term commitment on an AT&T customer account, and they need to have fulfilled their contract term, upgraded under one of our upgrade policies or paid an early termination fee."

In other words, as long as the iPhone you want to unlock is gathering dust in a drawer somewhere, AT&T will probably unlock it. If you or your business bought an iPhone 4S once it became available in October, you can't unlock it. It's probably still under contract. This policy is more likely to apply to the iPhone 4 (but probably only if you upgraded to the iPhone 4S), iPhone 3GS, iPhone 3G, and the original iPhone (if you still have that old hunk of smartphone history laying about).

The process to get the old iPhones unlocked is fairly simple: Call AT&T or go to an AT&T store, give them the IMEI number, wait for an email from Apple with the necessary code and instructions, follow the stops, and voila, you now have an unlocked iPhone.

What does this do for you, and more importantly, does this do anything for your business?

Nearly every smartphone is locked to the carrier that sells it. Locked devices can only be used on a particular carrier's network, meaning a device you buy from AT&T can't be used on T-Mobile's network and vice versa. However, many phones can also be unlocked. Customers willing to spend a few moments on the phone and (sometimes) pay a fee, could get their devices unlocked. Some carriers require that the user fulfills 60 days of the contract before agreeing to unlock the device, but AT&T has never agreed to unlock the iPhone.

For example, in 2008, I upgraded from the original iPhone to the iPhone 3G. After switching devices, I noticed that my old iPhone couldn't be used with other carriers. Even though I had purchased the device for full price, AT&T and Apple wouldn't unlock it. Basically, the device had been downgraded to an iPod Touch. I was furious. That iPhone was 100% my property. How dare they keep it locked!

Unlocked phones can be used on the networks carriers other than the one that sells it. For the iPhone--especially the older GSM-only models--this means you can take your old iPhone to any carrier (such as T-Mobile USA), buy a SIM card, and enjoy wireless service. In T-Mobile's case, the iPhone doesn't support its 3G network, but can still use T-Mobile's EDGE 2.5G network. In fact, many people do this (after jailbreaking their devices).

Now that AT&T and Apple will officially unlock old iPhones, you no longer have to jailbreak an iPhone to use it on the carrier of your choice.

For business users, this isn't all that relevant. Most business users are probably signed to current contracts and can't unlock their current devices. The chief benefit of having an unlocked phone is so that it can be used on other networks. You've always been able to use the AT&T SIM card from an iPhone in another AT&T device and use AT&T's services. That doesn't change.

The one important factor, however, is security. Jailbreaking iPhones creates security holes that can be breached. (Businesses shouldn't allow employees to jailbreak their devices in the first place.) Now that jailbreaking is no longer required, IT can breath a sigh of relief knowing that at least one avenue has been roped off.

The bottom line here is the following: Old iPhones are now slightly more useful, because they can be used on networks other than AT&T's. Who does this benefit? People who actually have old iPhones on hand. Most business users probably don't. It also means the secondary market for used iPhones just got more exciting, something else that most businesses shouldn't care all that much about.

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