Dual-SIM - definition
This specifies whether a device is capable of supporting two SIM cards. The two major types of dual-SIM phones are active and standby. Dual-SIM Standby (DSS) requires the user to specify which of the two SIMs is able to make and receive calls, while Dual-SIM Active (DSA) enables both cards to receive calls at the same time. This latter feature usually requires an additional transceiver for the secondary SIM card, and as such consumes more battery life. More recent models feature Dual SIM Dual Standby (DSDS) technology which enables them to have two active SIMs with only one transceiver.