Patent ID: 8208961

Claim:
A system for operating at least two subscriber identity cards, comprising: a subscriber identity module (SIM) controller, after being power-on, generating a first voltage variable signal with a first voltage level to a first subscriber identity card during a first time period, generating the first voltage variable signal at a second voltage level to the first subscriber identity card during a second time period, receiving a first code indicating that generated voltage matches from the first subscriber identity card during the first or second time period, generating a first operating voltage with the first voltage level to the first subscriber identity card when receiving the first code in the first time period, generating the first operating voltage with the second voltage level when receiving the first code in the second time period, generating a second voltage variable signal with the first voltage level to a second subscriber identity card during a third time period, generating the second voltage variable signal with the second voltage level to the second subscriber identity card during a fourth time period, receiving a second code indicating that generated voltage matches from the second subscriber identity card during the third or fourth time period, generating a second operating voltage with the first voltage level to the second subscriber identity card when receiving the second code in the third time period, and generating the second operating voltage with the second voltage level to the second subscriber identity when receiving the second code in the fourth time period, thereby enabling the first subscriber identity card and the second subscriber identity card to be operated at the first voltage level and the second voltage level respectively.