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A dual Subscriber Identity Module (SIM) Global System for Mobile communications (GSM) phone is a wireless phone that allows its owner to simultaneously use two SIM cards. This type of phone allows users to associate two separate numbers with a single device. Dual SIM GSM phones can be considered standby dual SIM phones or active dual SIM phones.
Standby dual SIM phones usually work with adapters that let the average cell phone operate as a dual SIM phone. However, when using a standby dual SIM phone, only a single SIM can receive calls at a time. Users have to manually switch between SIM cards if they want to use a particular phone number.
On the other hand, active dual SIM phones allow users to receive phone calls at the same time. This eliminates the need to switch between SIM cards. Users are free to answer phone calls on either SIM as calls come in.
A dual SIM GSM phone is more practical than previous solutions to the problem of using two SIM cards with one phone. Dual SIM holders and dual SIM adapters, for example, were difficult to fit into phones and the switching between SIM cards could be tedious. Dual SIM GSM phones provided a simple answer by allowing two SIM cards to be placed into one phone and having them both be active at the same time.
Cell phone users who opt for dual SIM GSM phones usually have a need to keep two distinct numbers. For example, dual SIM phones can be used by someone who wants to use one SIM card for business and the other for personal use. Dual SIM card phones can also be used by those who travel and want to keep a domestic phone number and a phone number local to their destination.
Using a dual SIM GSM phone can have many advantages. Dual SIM phones may be able to help cell phone users manage their cell phone costs by making sure that the users always have local numbers from which to place and receive calls. Cell phone owners who want to use two phone numbers can also enjoy the freedom of only having to carry one cell phone.
In addition, each SIM card used within the cell phone can be associated with a different carrier. While American GSM phone carriers have proven hesitant to make dual SIM GSM phones ubiquitous, American cell phone users can easily find a way to use dual SIM GSM phones. They may simply purchase an unlocked phone that is compatible with their carrier and their country's GSM frequency bands.