ECUs Explained

What is an SP Lock/Sim Lock?
Why are phones Sim Locked?
How can I figure out if my mobile phone handset is Sim Locked?
Is my handset barred?
How can I get the SP lock removed on my handset?
What other locks are there on mobiles?

What is an SP Lock/Sim Lock?
Every mobile phone handset has various locks. The SP lock (SP stands for ‘service provider’) prevents the user from using any other network sim card other than the one the phone is locked to. It is also sometimes referred to as a network lock or sim lock. From hereon we will refer to it as a sim lock for simplicity. This lock is not to be confused with other locks you come across on mobile phone handsets.

Why are phones Sim Locked?
Many phones are sold at heavily discounted prices, effectively subsidised by the network that the phone is sold with. They intend to get a return on their subsidy by ensuring the user sticks with their network.

How can I figure out if my mobile phone handset is Sim Locked?
Enter a sim card from a network different than the phone currently uses. Just because you place a sim card in a handset and it fails to work do NOT assume that the phone is sim locked. There may be various other reasons why it won’t work. For instance, if the phone turns on and there is simply no signal and no other messages shown then the phone is NOT sim Locked. Likely explanations for that condition would be - there is no network coverage available in that particular area; the phone’s hardware does not work on the specific frequency for that airtime provider (see here); the phone is barred (reported stolen/lost). Different manufacturers have different messages to show a phone is sim locked. Typically you’ll get the following messages with these manufacturers:
Nokia - Insert Correct Card or Sim Card Rejected
Motorola - Enter Special Code
Ericsson - Wrong Card
Sony Ericsson - Incorrect Sim
Panasonic - Invalid Sim
Samsung - Network Locked - Enter Password
Siemens - Phone Disabled
LG - Insert Right Card

Again, some of these messages do not guarantee that there is a sim lock. For instance a Nokia handset may say Sim Card Rejected because the handset is barred or a Siemens model may say Phone Disabled because you’re entering an old 5v sim while that handset may only accept late 3v cards. Note though that old 5v sim card are quite rare. Unless you’ve had the same sim for at least 5 years then it’s unlikely to be the old 5v card.

Is my handset barred?
Airtime Providers can bar a handset but this varies from one network to another. Some networks will only bar handsets if they are reported stolen/lost while some will bar a handset that has not been honoured in it’s contract as well. In the UK, due to government pressure, all networks now bar handsets and once one network bars the handset it is barred across all networks in the UK. Each handset has a unique electronic serial number called the IMEI (International Mobile Equipment Identity). This IMEI is placed on the blacklist so when the handset makes communication to the network the phone receives communication back that it is blocked. Some handsets will actually come up with a message to reflect this while some will just not go into service or give a 'dead line' tone when a call is attempted.

How can I get the SP lock removed on my handset?
Okay, you want to use another network sim in your handset from the one that it is locked to. Before you waste your time and money getting this done make sure the handset is compatible with the network you want to use by checking that the phone hardware will actually support that network frequency.

The correct (and safest) procedure for removing an SP lock is to enter the correct unlock code into the phone - this code is unique to every individual handset (normally working from an algorithm of the serial number (IMEI). You can normally obtain this code from the network that provided the phone subject to it’s history. They will normally not entertain code requests for handsets that have not been used with their network for at least a year (understandably). The network companies will charge for this code - approx £35 in the UK.
The alternative to get this code is from various third party companies offering unlocking services over the net or phone. For a fixed they will provide your unlocking code once you provide them with your phone’s details including the IMEI of the handset and which network it is currently locked to. Ensure that you are dealing with a reputable company. These third party companies will only be able to supply unlock codes for certain models and certain software versions. Where an unlock code cannot be supplied many models can be unlocked via software and a data lead plugged into the handset. These software solutions vary between original manufacturer software and third party software written by independent programmers. Always beware of software solutions because some can take a very unorthodox route to removing the sim lock which may affect certain features of the phone. The phone’s software may be downgraded or settings altered which ruin reception strength or battery life. This is normally because the programmer has not cracked the proper solution and instead effectively clones the phone with the data from an unlocked handset. Whether you are sending your phone off or taking it to a mobile phone retailer always ask them how they will be unlocking the phone and whether the phone software will be altered in any way. If all your user data is wiped from the phone then that is a good indication that the software has been re-written. While this may not necessarily affect the phone’s performance it certainly won’t be the best solution for unlocking the handset. Another thing to ask is whether the phone will be unlocked on site or handed to a third party. Many handsets, especially late models, will go through various hands and the retailer may not be aware of exactly how the handset will be unlocked.
If there isn’t a code or plug-in solution for a handset then the last resort is normally opening the handset and accessing the circuitry direct. Many of the late Sagem models are currently done this way.

What other locks are there on mobiles?
A handset lock is simply a lock set by the user to provide some security for use of the handset. When the phone is initially turned on it will prompt for this code and once entered the phone will continue and go into service etc. This lock is usually not active as standard and the user has to activate it. The user can also change the handset lock to their own custom code.
A pin code is a lock placed on the sim card. Again, by default, it will not be present unless activated by the user and can be custom set to the user’s code.

Note: All text here is original and copyright. I've had previous articles stolen (copied verbatim) and pasted on other websites. I've spent a lot of time composing these articles - they are not here for lazy people to steal.

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