Dual subscriber identity module (SIM) mobile phones are phones that can use two SIM cards at once, which results in there being many factors to look at when choosing the best phones. There are several types of dual SIM mobile phones based on how they access the SIM cards, because the cards can be accessed at the same time or through the user selecting which card to use. Along with using two SIM cards, some dual SIM mobile phones also have dual Bluetooth®, so each SIM card can wirelessly control or integrate with other devices. These phones tend to use more energy because of the two SIM cards, so battery life should be considered. Sound quality also may suffer with two SIM cards, which may be worth considering.
While there are many types of dual SIM mobile phones, the two most common are active and manual SIM phones. Active means the mobile phones are able to access both SIM cards at once, so they are both on. This means a phone with one SIM card for work use and another for home use will have both active all the time. Manual phones require the user to select which card is active when, and the other is temporarily turned off.
The most defining aspect of dual SIM mobile phones is their ability to access two SIM cards, but some models also can use dual Bluetooth®. This enables the user to control Bluetooth® devices with each SIM, which may be useful depending on the user’s needs or phone contracts that limit Bluetooth® usage. There also is active and manual technology with Bluetooth® access.
In most cases dual SIM mobile phones — especially active phones — tend to use more power, because working with both cards at once requires power. The generally means the user should check on battery life, because phones with a short battery life may not be useful. It normally is best to find phones that can function for more than a day; continuous use otherwise may be difficult.
Sound quality can be an issue with some dual SIM mobile phones, because the SIM cards may interfere with each other. This most commonly affects earlier dual mobile phones, but it can still be a potential problem in more contemporary phones as of 2011. Finding a phone that has clear sound quality while still accessing both SIM cards usually is important, because poor sound quality can make it difficult to use this type of phone.