A device, comprising: a serial communication port comprising a carrier detect (CD) pin and a ring Indicator (RI) pin; a voltage selection unit (110; 210) configured to toggle between a first voltage and a second voltage based on input from a basic input/output system, BIOS; and a power unit configured to output either the toggled voltage or no voltage to both the carrier detect (CD) pin and the ring Indicator (RI) pin of the serial communication port based on the input from the BIOS; wherein, the input from the BIOS includes a first select and a second select, the voltage selection unit (110; 210) is configured to toggle between the first and second voltages based on the first and second selects, and the power unit is configured to output either the toggled voltage or no voltage based on the first select; wherein the voltage selection unit (110; 210) is configured to select the first voltage if at least one of the first and second selects is at a logic low, and the voltage selection unit (110; 210) is configured to select the second voltage if the first and second selects are at a logic high; and wherein the voltage selection unit (110; 210) includes a first transistor, a second transistor, a third transistor, a fourth transistor and a first node, wherein the first voltage is connected to a source of the first transistor , the first node (N1) is connected to a gate of the first transistor , a base of the second transistor , a gate of the third transistor , and a collector of the fourth transistor , the second voltage is connected to a source of the third transistor , a collector of the second transistor , an emitter of the fourth transistor and the first node (N1), and wherein an emitter of the second transistor is connected to a ground. a serial communication port comprising a carrier detect (CD) pin and a ring Indicator (RI) pin; a voltage selection unit (110; 210) configured to toggle between a first voltage and a second voltage based on input from a basic input/output system, BIOS; and a power unit configured to output either the toggled voltage or no voltage to both the carrier detect (CD) pin and the ring Indicator (RI) pin of the serial communication port based on the input from the BIOS; wherein, the input from the BIOS includes a first select and a second select, the voltage selection unit (110; 210) is configured to toggle between the first and second voltages based on the first and second selects, and the power unit is configured to output either the toggled voltage or no voltage based on the first select; wherein the voltage selection unit (110; 210) is configured to select the first voltage if at least one of the first and second selects is at a logic low, and the voltage selection unit (110; 210) is configured to select the second voltage if the first and second selects are at a logic high; and wherein the voltage selection unit (110; 210) includes a first transistor, a second transistor, a third transistor, a fourth transistor and a first node, wherein the first voltage is connected to a source of the first transistor , the first node (N1) is connected to a gate of the first transistor , a base of the second transistor , a gate of the third transistor , and a collector of the fourth transistor , the second voltage is connected to a source of the third transistor , a collector of the second transistor , an emitter of the fourth transistor and the first node (N1), and wherein an emitter of the second transistor is connected to a ground. <EOS>