A Global System for Mobile Communication Subscriber Identity Module, or GSM SIM card, is a SIM card that uses the GSM network. Having this card in an unlocked cell phone while using the correct frequency allows a cell phone user to use his cell phone in various countries all over the world. The GSM network is the network used by most countries in the world, allowing cell phone users to carry their phones from country to country. This network is not the primary network used in countries such as the United States, which is why many US residents have trouble using their phones overseas.
To use a GSM SIM card, a user will need an unlocked phone—that is, a phone that is able to use SIM cards from different phone carriers—that uses the GSM network and works at the frequency the destination country uses. In many European countries, that frequency is 900 MHz or 1800 MHz. A phone that uses the proper frequency is important because even if a phone can use the GSM network, if it is not on the correct frequency, it still won’t work. Once a user has an unlocked phone that will work with the GSM network as well as the correct frequency, he can use the GSM SIM card. This card allows the user to use the same phone number internationally, no matter which country he is in.
Having a GSM SIM card allows a person to use the same cell phone in different countries rather than having to buy a new SIM card or phone whenever they travel internationally. This is ideal for those who travel often or want to be able to use their phone while on vacation. Since the SIM card holds the user’s phone number and information, the chip can even be used on another person’s international phone, while still billing the owner of the SIM card. This allows a person to either buy a phone of his own or rent one from an appropriate carrier.
If a person does not have the appropriate phone for a GSM SIM card, it is possible to rent an international phone. This is possible because he can insert the chip in various phones and use them in different countries. The information stays with the SIM card so the user can simply pay a fee to use a compatible phone of his choice while traveling in a different country. This allows him to use the phone without paying his domestic carrier’s roaming charges. Renting a phone allows someone to get a phone when they do not wish to or are unable to use his phone overseas.