Mobile phone carriers commonly subsidize the costs of new cell phones. The customer pays $99 for a five hundred dollar phone and the carrier pays the rest of the cost. The customer signs a service contract where the customer agrees to stay with the service provider for a number of years. Over the lifetime of that contract, the mobile phone service provider makes enough profit to cover their initial subsidy on the purchase of the cell phone.

To ensure that the customer uses the mobile phone on their network, many cell carriers will "lock" the cell phone so that it can only be used on their network.

This lock is referred to as a Service Provider Lock (SPL), a network lock, or a subsidy lock.

When your service contact expires and you want to switch cellular carriers, you may have to "unlock" your phone. If you purchase a used cell phone, you may also have to unlock that phone.

Unlocking the mobile phone will allow you to use it on another carriers network.

How to Unlock a Phone

Techniques for unlocking a phone vary between phone models and between carriers.

Ask Your Carrier for the Unlock Code

Some carriers will tell your your unlock code. They may require your account to be paid up, your account to be a certain age, or your service contract to be expired. Other carriers will never tell you your unlock code under any circumstances.

?Sprint refuses to provide unlock codes to their customers

?T-Mobile will provide unlock codes to their customers after the subscription has been active for 90 days

?AT&T/Cingular CDMA phones are shipped unlocked

?AT&T/Cingular will provide unlocking codes for their GSM phones

Once you have the unlock code, you can enter it on your phones keypad. Some providers are able to unlock phones remotely over the air.

Calculate the Unlock Code

Some providers use unlock codes which are calculated from the IMEI of the mobile telephone.

For example, the unlock codes for some Nokia phones can be discovered using the online calculator at Nokia Free.

LG Unlocking Calculator performs a similar service for LG cell phones.

The Ultimate Calculator calculates unlock codes for some Nokia, Panasonic and Siemens cell phones.

Universal SIM Lock Remover is a shell which calls programs to unlock phones from Alcatel, Benq, Ericsson, LG, Motorola, Mitsubishi, Maxon, NEC, Nokia, Panasonic, Philips, Samsung, Sendo, Sharp, Siemens, SonyEricsson, Toshiba, Vitel and VK.

Some mobile service providers now use random unlock codes. These codes cannot be calculated.

Use a Clip to Unlock the Phone

If your mobile service provider will not help you and you cannot calculate the unlock code for your cell phone, you may be able to unlock your mobile phone with a clip.

A clip, in this context, is a cable which connects your cell phone to your PC. You then install software on your PC which reprograms the mobile phone to remove the lock entirely.

Use a Service to Unlock the Phone

If you don't want to unlock the phone yourself, or you don't want to buy a clip, there are services available who will unlock your phone for a small fee.