Dual-SIM mobile devices allow for the simultaneous use of two SIM cards. This feature is often chosen by users who would like to keep separate business and personal phone numbers, as well as by those who want to benefit from lower prices for calls between the same service provider. Another reason for choosing a dual-SIM gadget is to have more comprehensive coverage in certain areas or when traveling across borders.
Although dual-SIM is the norm in several countries, phones with only one SIM card slot are standard in other regions. For this reason, numerous smartphones have different versions with one or two SIM slots for diverse markets. Pressure from telecommunications companies has been listed as the main reason why single slots are still standard in some regions.
Devices with two SIM card slots may be divided between passive, standby, and active. Passive models function as single-SIM models, as only one SIM card is active at a time. The advantage here is the ability to switch between providers without the need to open the device's tray and change cards. The next type of dual SIM product, dual standby, works by making one channel unavailable while the other one is active. As an example, the user cannot receive a phone call placed to their secondary SIM while already in a call through the other channel. There are no such limitations when it comes to active dual-SIM models; this, however, comes at the cost of increased battery consumption, since the device must be equipped with two transceivers.
As already mentioned, plenty of smartphones (from flagships to budget phones) offer two sim card slots. When buying a phone via carrier contract, dual SIM models are hardly ever available, as telecommunications companies want to prevent users from using competing services.