Dual SIM Phones Supporting Dual Standby: It was very normal for one cell phone to accommodate a piece of SIM card. However, that happened before. Since the birth of dual SIM dual standby mobile phones, one SIM cell phones will be out of date soon. Dual SIM dual standby mobile phones satisfy with the needs and requirements of one machine more SIM cards to many businessmen in the fast-paced commercial society. You can insert two SIM cards (some cell phones have even 3 SIM card slots) into one cell phone, and the two SIM cards are on line simultaneously, needless to switch between them. Surely, if you only want one of them is on line, you can set it in menu, as dual SIM dual standby mobile phones support four modes (dual SIMs, SIM1, SIM2, Flight mode). Besides, most dual SIM dual standby phones at onThesource.com support dual Bluetooth, you can phone and listen to music via Bluetooth devices.