An apparatus comprising: a first connection (15, 16) to a battery; a second connection (20, 21) to an external subscriber identity module card; a first path between the first and second connections including a non-upconverting voltage regulator and being absent of a buck/boost converter; a second path between the first and second connections including a buck/boost converter; and a controller configured: to determine a battery voltage of the battery connected at the first connection; to send a request for information about the subscriber identity module card to the subscriber identity module card via the second connection; to determine from information received from the subscriber identity module card a minimum operating voltage of the subscriber identity module card; to determine whether the battery voltage provided at the first connection exceeds a threshold that is greater than the minimum operating voltage of the subscriber identity module card; and on a positive determination, to enable the first path and disable the second path; and on a negative determination, to disable the first path and enable the second path wherein the controller is further configured to determine the minimum operating voltage of the subscriber identity module card by determining a type of the subscriber identity card and in response to a determination that the subscriber identity module card is a 1.8V type subscriber identity module card, causing the connection from the battery to the subscriber identity module card via the non-upconverting voltage regulator and without a buck/boost converter. a first connection (15, 16) to a battery; a second connection (20, 21) to an external subscriber identity module card; a first path between the first and second connections including a non-upconverting voltage regulator and being absent of a buck/boost converter; a second path between the first and second connections including a buck/boost converter; and a controller configured: to determine a battery voltage of the battery connected at the first connection; to send a request for information about the subscriber identity module card to the subscriber identity module card via the second connection; to determine from information received from the subscriber identity module card a minimum operating voltage of the subscriber identity module card; to determine whether the battery voltage provided at the first connection exceeds a threshold that is greater than the minimum operating voltage of the subscriber identity module card; and on a positive determination, to enable the first path and disable the second path; and on a negative determination, to disable the first path and enable the second path wherein the controller is further configured to determine the minimum operating voltage of the subscriber identity module card by determining a type of the subscriber identity card and in response to a determination that the subscriber identity module card is a 1.8V type subscriber identity module card, causing the connection from the battery to the subscriber identity module card via the non-upconverting voltage regulator and without a buck/boost converter. to determine a battery voltage of the battery connected at the first connection; to send a request for information about the subscriber identity module card to the subscriber identity module card via the second connection; to determine from information received from the subscriber identity module card a minimum operating voltage of the subscriber identity module card; to determine whether the battery voltage provided at the first connection exceeds a threshold that is greater than the minimum operating voltage of the subscriber identity module card; and on a positive determination, to enable the first path and disable the second path; and on a negative determination, to disable the first path and enable the second path wherein the controller is further configured to determine the minimum operating voltage of the subscriber identity module card by determining a type of the subscriber identity card and in response to a determination that the subscriber identity module card is a 1.8V type subscriber identity module card, causing the connection from the battery to the subscriber identity module card via the non-upconverting voltage regulator and without a buck/boost converter.