Updated

Now that the U.S.Copyright Office has given a green light to unlock your GSM or iDen cell phone (click here for details) you can save money on a new phone — provided you can find it unlocked, or unlock it yourself.

Depending on your phone, you might be able to do that by punching in a code, by buying a cable or by sending it to a professional unlocking service.

This applies to Cingular Wireless, T-Mobile and Nextel phones; Sprint, Verizon Wireless and Alltel subscribers are out of luck, for reasons I'll explain below.

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If you've had a T-Mobile phone for 90 days, or you've run out of time on a Cingular contract, you can get an unlocking code just by calling your carrier.

Tell your carrier's customer service representative that you're traveling abroad and want to use a foreign carrier's SIM card. If they don't give you the code, stick by your guns and ask for a manager.

If you don't fulfill those requirements — say you've just bought a phone off of eBay and it turns out to be locked, or you want to use a phone locked to a foreign carrier, or you want to make a prepaid phone into postpaid — you have a bunch of different options.

If you have an older or more basic Nokia phone, including the 1100, 6230, 6820 or 7650, you can use a free, online calculator to figure out your unlock code.

Check out the instructions at http://nokiafree.org/forums/t64045/s.html and then use the calculator at http://unlock.nokiafree.org/ to find the code.

Owners of a few GSM Pocket PC smart phones made by HTC — the Cingular 8125 and 8525, and T-Mobile MDA — can use another free tool, at http://forum.xda-developers.com/showthread.php?t=240784.

For most other phones, you have to buy something, whether it's software or a service.

Many phones, including Sony Ericsson phones, BlackBerries, some Treos, some LG phones and HTC smart phones can be unlocked with software and a special cable, according to Alex Parkhomovich of http://www.CellCorner.com in Astoria, N.Y.

Running the software taps into a remote database of unlocking codes and transmits the right code to your phone. All told, expect to spend $15-60 for the cable and/or the license to unlock one phone.

Many more recent phones either require hardware modifications or aren't unlockable at all, according to Evan Silbert, president of Warlocks Wireless (http://www.iunlock.com) in Boston.

Silbert only does "postal unlocking" — you send him a phone, he unlocks it and sends it back to you, charging around $25 for the service.

Postal unlocking is the best bet for non-expert users, Silbert says, because he guarantees success and his experts won't damage your phone.

On recent Motorola phones, that involves disassembling the phone, drilling into a shield over the main circuit board to tap into the right contacts and kicking the phone into a special diagnostic mode to get at the unlocking code.

Recent Samsung phones can be unlocked with a software-only process, Silbert said.

If you're really hardcore, you can buy gadgets like the NsDongle for unlocking Samsung phones and the Smart Unlocker box for many Motorola phones from CellCorner.

But that kind of unlocking hardware costs $200 or more, so Parkhomovich suggests buying unlocking software or services instead, which cost $15-60 from him, depending on the device.

Unfortunately, some very new phones can't be unlocked at all. The hackers are working on it, but if you can't find your phone on the lists at CellCorner, iUnlock, or other unlocking shops like http://www.TheFoneDoc.com and http://www.GSMLiberty.net, you may be out of luck.

Once your phone is unlocked and moved to a different network, you'll have to reprogram the phone's data settings so you can access the Web and send and receive picture messages.

T-Mobile users can get their settings at http://tmobileus.wdsglobal.com/phonefirst; Cingular users should call 611 and ask to have their MMS and WAP settings pushed to their phone number.

The various unlocking services all unlock different phones for different prices, so it's worth shopping around to find the best service and the best deal. HowardForums has a good list of unlocking shops (http://www.howardforums.com/forumdisplay.php?f=63).

No Love for CDMA

All of this only affects GSM and iDen phones — in other words, Cingular, T-Mobile, Nextel and Boost phones.

CDMA phones, used by Sprint, Verizon Wireless, Virgin Mobile, Amp'd, Helio and Alltel, have more security, according to Ron Piazza, a communications specialist for Valley Tel Service in Eugene, Ore.

CDMA phones have handset locks and also have to be individually authenticated by their networks.

So even if you unlock a CDMA phone, it won't work if it isn't on the serial number list of the network you're bringing it to. The carriers won't add individual new serial numbers to their databases.

Representatives of Sprint and Alltel said that banning other carriers' phones protects the user experience on their networks.

"We think it's important to optimize the customer experience by making sure all of the handsets on our network are optimized for it," said Sprint spokesman Travis Sowders.

That's corporate double-speak, to some extent. Even though Sprint, Verizon and Alltel all sell Motorola V3m phones, for instance, they won't activate each other's V3m's, and although carriers individuals can "flash" CDMA phones with the software sets from other carriers, the carriers just choose not to.

Piazza said he used to be able to activate various phones on Verizon's and Alltel's networks. But both carriers have cracked down recently.

Verizon, Alltel and Sprint all say they absolutely will not activate any phones that aren't already in their databases.

A few hackers can get around that by copying an approved serial number into a phone, Piazza says.

Unfortunately, that's against the law — not the DMCA, but a 1997 law that specifically forbids "cloning" phones.

Like many wireless users, Piazza finds that frustrating.

"You're buying a product, not leasing the product. After you fulfill your [contract] agreement and the phone is yours, why should that phone be useless to you?" he asks. "Why should it be locked to a specific provider?"

Copyright © 2006 Ziff Davis Media Inc. All Rights Reserved. Reproduction in whole or in part in any form or medium without express written permission of Ziff Davis Media Inc. is prohibited.