SIM Unlocking

Many mobile phones have a Subscriber Information Module (SIM) that identifies the phone as belonging to one service provider in a particular country. These phones are programmed to work with certain SIM cards before they are purchased. SIM unlocking will change that programming either by entering a code into the phone or by changing the software. Changing the cards will enable one phone to work in different countries or with the services of different providers. A mobile phone owner can benefit from SIM unlocking because he or she can still use their phone after changing providers, or keep the old phone in case something goes wrong.

If a phone or card has not been unlocked by the company, there are a couple of ways it can be done. A code, which identifies the phone’s serial number, is typically required for SIM unlocking. Codes can be found for specific models of phones and are sometimes sold by service providers or other companies. If the phone’s software needs to be changed, then a specific cable and machine to program it are needed. This process can also be provided as a service performed for a fee.


Phones are programmed to alert users if a restricted SIM card is put in. Swapping cards will determine whether a particular phone is unlocked. If a code or software upgrade has unlocked a phone, there should be a message that says so once the procedure is completed. Another way SIM unlocking can be done is to send the phone to the manufacturer or phone company, which is generally completed for a fee.

In some cases, companies will unlock phones when they are purchased. If the phone is unlocked later by the user, then the warrantee may be voided and the company will no longer service the phone. The SIM unlocking technology, however, does not do anything to change the function of the phone or improve the reception. If a phone user changes providers, there is the chance that a new service company can re-lock the phone, even though the device doesn’t belong to the company.

In the past it was considered illegal by some regional authorities, but SIM unlocking is often legal to perform as of 2011. It is occasionally beneficial to use a different SIM card, especially if the phone is used in another country than where the user lives. Users can also keep their phones even when changing providers. An unlocked SIM card also lets a someone keep the old phone as a backup, so he or she can insert the card in that device if something goes wrong with the first.

Unlocked GSM Smartphones

Unlocked GSM smartphones are personal electronic devices. They are designed for use on the most common type of cellular phone network, those that use the Global System for Mobile Communications. The term ‘unlocked’ means the phone is not restricted to the network of a particular cellular provider, but can be configured to work on any network that employs the GSM standard. As smartphones, they are able to act as telephones, but have additional functionality because of their ability to serve as mobile internet access points.

There are several different network standards for cellular communication. Most of the world uses the GSM standard. The United States is the most notable exception to this rule. Some cellular providers in the United States do employ this technology, but it is only one of several network standards in use.

All GSM devices, including unlocked GSM smartphones accept a subscriber identity module card, or SIM card. This small memory card stores information for a phone’s user, and allows that information, and any linked account, to be easily transferred between devices. Often, cell phone service providers will place a hardware or software locking feature in their devices, so that those devices can function on only their network.


Mobile devices may be purchased, generally for a greater fee, without such restrictions. Unlocked GSM smartphones either never had such a lock, or have had it disabled. As a result, they can be freely transferred between networks, will accept any SIM card, and will function normally so long as that SIM card is associated with an active and valid account. Unlocked GSM smartphones are, as a result of this feature, very portable, and allow their users to change carriers easily, without needing to replace their handsets.

Like all smartphones, unlocked GSM smartphones have additional capabilities beyond those available on ordinary handsets. Modern smartphones combine the normal functions of mobile telephones with the features of PDAs. Smartphones also use cellular networks, and often wifi hotspots, to access the Internet.

The functionality of smartphones can also be greatly expanded through the installation of applications, or apps. These small programs take advantage of the internet connectivity, the user's position, and other information provided by the cellular network to offer additional utility to users. Although unlocked GSM smartphones are portable between networks, some apps are proprietary, and not fully portable between different service providers.

GSM Wireless Network

A Global System for Communications (GSM) network is a series of virtually interconnected tower and satellite relays that send and receive digital signals allowing people to communicate wirelessly across the globe. The signal begins with a cell phone that places a call, and travels to the nearest GSM tower. That tower communicates the signal to a satellite, which in turn relays that signal to the tower nearest the call's destination, where it is then received by the call recipient. The GSM wireless network is the most popular wireless communications system today.

Original cell phone technology operated on an analog system, similar to a short-distance radio wave. This meant that many people could use the same frequency, but the frequency would vary by location. During the 1990s, new wireless licenses were made available, and as carriers built their own networks, the switch was made to digital signals.

The digital communications networks were carriers for Second-Generation (2G) cell phone technology, which featured less call interference and increased call security, owing to the digitized signal. The phone's batteries lasted longer, and more calling features could be offered since the network was expanded. The biggest advantage, however, was that the efficiency of digital capacity lowered the startup cost of a new carrier, allowing smaller players to join the industry and offer real competition that leads to lower service prices.


As digital communications evolved and networks developed, standards were set that would allow towers to transmit the signal from any carrier, regardless of which carrier the tower belonged to. Thus began the GSM wireless network, which currently operates in 900 megahertz and 1.8 gigahertz bands in Europe, and 850 megahertz and 1.9 gigahertz bands in the United States, Canada, Australia, and South America. The adoption of uniform standards allows cell phones to operate abroad the same as they do at home.

The GSM wireless network system currently boasts coverage in 218 countries, serving over 3.8 billion customers. There are very few areas where GSM coverage is unavailable — usually very remote, rural areas — and specialized satellite roaming features are available to cover any gaps in coverage. The 89% market share of the GSM network means that new mobile technologies are usually created in accordance with GSM standards, and the GSM wireless network technology has evolved along with it.

GSM now carries Third Generation (3G) cell phone service as well as Fourth Generation (4G) technology, which allows users to transmit larger amounts of voice and data streams simultaneously. Each new incarnation of GSM service is compatible with each version that came before, eliminating the need for customers to upgrade their phone each time new technology is released.

Test a Network Card

The usual reason individuals test a network card is to find out if it is working properly and if it is letting the computer access other devices or networks. One of the easiest ways to test a network card is by sending a ping to a website that is known to be always up most of the time. You can also test a network card by checking the properties section and the internet protocol (IP) configuration of your personal computer.

When sending a ping to a website to test a network card, it is best to choose one of the most popular websites because they are likely to be up most of the time. The popular search engines are examples of these kinds of websites. This can be done by opening the computer's command line. From the command line, you simply type the word ping, then a space and the uniform resource locator (URL) of the web site, and hit enter.

You will then see results of the ping you sent. These results frequently display the response time, the number of packets sent, the number of packets received, and the number of packets lost. If you get these numbers, it means you have a working network card. Any other results may indicate that the website you are pinging is down or your network card is not working.


Another way to test a network card is to check your device properties to see the status of your network card. With most computers, you can do this by going to the device manager and opening the properties window of the network card you want to test. It often tells you if the device is working properly. If this message does not appear, you can check the status or even reinstall the network card's device driver.

You can also test the IP configuration of your computer if your network does not seem to be working. By looking at the IP configuration of your computer, you can see the IP of your network card. If values are set in the section of the network card IP, it usually indicates that the network card has been installed properly. These values can be verified by testing the connection. Sending a ping to a reliable website is frequently good way to verify that these values are correct.

There are several types of network cards. These include an integrated network card, a local area network (LAN) card and a mini network card. Each of these network cards include network card software that you can use to install, troubleshoot, and test a network card. Several diagnostic tools included in these packages can be utilized to make sure that your network card is working properly.

Subsidy Lock

A subsidy lock is a physical feature on a mobile telephone that restricts which SIM cards it will work with. Though there are other names for the technology, the subsidy lock usually refers to a phone being restricted to operating on a particular network. This is because such phones are usually sold at a low price, with the network paying a subsidy to the manufacturer.

The subsidy lock works with the GSM communications system, the most common type of mobile telephone around the world. It restricts the SIM cards that will work in the phone. The SIM card connects the phone to a particular network, and without it, the phone cannot make or receive calls, with the exception of emergency services calls in some countries. These restrictions can cover the country where the SIM card comes from, the network providing the SIM card, or both. It's also possible to restrict a phone to a single SIM card.


Usually the phrase "subsidy lock" refers to a restriction on a network. This is because many networks, particularly those that sell phones themselves, will pay a subsidy to manufacturers, meaning the purchase price for the consumer is lower than it would otherwise be, and may even be below cost price. In return for this subsidy, the network will attempt to avoid the consumer using it with another network. While this can sometimes be achieved by a mandatory service agreement, a subsidy lock is needed to stop a pay-as-you-go customer from getting the phone cheaply and then taking his business elsewhere.

In most cases, a subsidy lock can be removed by typing in a code. Some networks will provide this code in return for a fee. This fee is designed to cover the loss of income from future phone use. In some cases, the algorithm that converts the unique identity code of the phone, known as the IMEI number, to the unlock code has been leaked or stolen. This allows independent companies to provide unlock codes to phone users at a lower price than the network charges.

The legal position on subsidy locks and unlocking varies across different countries. In the United States, as of 2010, phone unlocking was specifically exempted from the Digital Millennium Copyright Act. This means that it is legal to unlock a phone and run it on any network. Some networks warn that doing so voids any warranty on the handset. It's important to note that although a contract customer may be able to legally unlock a phone, he will usually still be required to pay for the service from the original provider for the duration of the contract.

Unlocked GSM Smartphones

Unlocked GSM smartphones are personal electronic devices. They are designed for use on the most common type of cellular phone network, those that use the Global System for Mobile Communications. The term ‘unlocked’ means the phone is not restricted to the network of a particular cellular provider, but can be configured to work on any network that employs the GSM standard. As smartphones, they are able to act as telephones, but have additional functionality because of their ability to serve as mobile internet access points.

There are several different network standards for cellular communication. Most of the world uses the GSM standard. The United States is the most notable exception to this rule. Some cellular providers in the United States do employ this technology, but it is only one of several network standards in use.

All GSM devices, including unlocked GSM smartphones accept a subscriber identity module card, or SIM card. This small memory card stores information for a phone’s user, and allows that information, and any linked account, to be easily transferred between devices. Often, cell phone service providers will place a hardware or software locking feature in their devices, so that those devices can function on only their network.


Mobile devices may be purchased, generally for a greater fee, without such restrictions. Unlocked GSM smartphones either never had such a lock, or have had it disabled. As a result, they can be freely transferred between networks, will accept any SIM card, and will function normally so long as that SIM card is associated with an active and valid account. Unlocked GSM smartphones are, as a result of this feature, very portable, and allow their users to change carriers easily, without needing to replace their handsets.

Like all smartphones, unlocked GSM smartphones have additional capabilities beyond those available on ordinary handsets. Modern smartphones combine the normal functions of mobile telephones with the features of PDAs. Smartphones also use cellular networks, and often wifi hotspots, to access the Internet.

The functionality of smartphones can also be greatly expanded through the installation of applications, or apps. These small programs take advantage of the internet connectivity, the user's position, and other information provided by the cellular network to offer additional utility to users. Although unlocked GSM smartphones are portable between networks, some apps are proprietary, and not fully portable between different service providers.

Network Coding

Network coding is a programming technique used to maximize the potential output of a computer network. In network coding, the nodes of the network take on an active role, working to combine and compress packets of information before sending them across the network. This enables a more efficient utilization of network resources, at the cost of additional overhead on the part of the client computers, which must work that much harder to "untie" the packed data.

Network nodes are a bit like traffic police: they direct the flow of data on a computer network. In the absence of network coding, the nodes move information — packets of data — through the network without taking liberties to alter or manipulate that data in any substantial way. They might reinforce the signal to ensure that data is not lost during transit, but the actual packets remain unaffected.


In network coding, the nodes are tasked with the job of combining packets as necessary to increase efficiency in the network. For example, if a network is capable of transmitting individual packets of 100 bytes and it receives two 50 byte packets at the same time, a system operating with non-network coding will process one 50 byte packet and then the next, moving them through sequentially. A network coding network, on the other hand, will register the fact that 50 bytes of potential network overhead are being "wasted" with each packet, and combine the two 50 byte packets into a single 100 byte packet, maximizing the network's data-transmission capacity.

This results in an increase in network efficiency. Network coding uses more of the network's available bandwidth on a regular basis. In other words, more of the network's potential is realized. However, network coding also has a downside: the combined packets provide additional "work" for the receiving computers.

When a computer receives a packet of information on a non-network coded network, the computer accesses that piece of information individually and immediately. Packets, in this case, are each entirely dedicated to a single process. Receiving a packet of information on a network coded network, however, requires the system to unpack and distribute information related to different processes to the proper areas. This creates extra processing responsibilities for the computer CPU receiving the data, increasing its stress. On low-powered systems, or systems with a number of other concurrently active tasks, the extra work can result in slowdown or lag on the computer.