A switched mode power supply (100, 200, 300) for communicating with a master controller of a power system, the switched mode power supply (100, 200, 300) comprising: an input; an output; a power circuit coupled between the input and the output; a communication interface including an address terminal configured to couple to an external resistor (Rx) for setting a communication address of the switched mode power supply (100, 200, 300) when the external resistor (Rx) is coupled to the address terminal; and a control circuit (110, 210, 310) coupled to the power circuit and the communication interface, characterised by the control circuit (110, 210, 310) configured to: set the communication address of the switched mode power supply (100, 200, 300) using a first technique if a value of the external resistor (Rx) is greater than a threshold value; set the communication address of the switched mode power supply (100, 200, 300) using a second technique if the value of the external resistor (Rx) is less than the threshold value; determine the value of the external resistor (Rx) a first time with the first technique; compare the first determined value of the external resistor (Rx) with the threshold value; and if the first determined value of the external resistor (Rx) is less than the threshold value, determine the value of the external resistor (Rx) a second time using the second technique and set the communication address based on the second determined value of the external resistor (Rx); wherein the control circuit (110, 210, 310) does not determine the value of the external resistor (Rx) the second time using the second technique if the first determined value of the external resistor (Rx) is greater than the threshold value. an input; an output; a power circuit coupled between the input and the output; a communication interface including an address terminal configured to couple to an external resistor (Rx) for setting a communication address of the switched mode power supply (100, 200, 300) when the external resistor (Rx) is coupled to the address terminal; and a control circuit (110, 210, 310) coupled to the power circuit and the communication interface, characterised by the control circuit (110, 210, 310) configured to: set the communication address of the switched mode power supply (100, 200, 300) using a first technique if a value of the external resistor (Rx) is greater than a threshold value; set the communication address of the switched mode power supply (100, 200, 300) using a second technique if the value of the external resistor (Rx) is less than the threshold value; determine the value of the external resistor (Rx) a first time with the first technique; compare the first determined value of the external resistor (Rx) with the threshold value; and if the first determined value of the external resistor (Rx) is less than the threshold value, determine the value of the external resistor (Rx) a second time using the second technique and set the communication address based on the second determined value of the external resistor (Rx); wherein the control circuit (110, 210, 310) does not determine the value of the external resistor (Rx) the second time using the second technique if the first determined value of the external resistor (Rx) is greater than the threshold value. set the communication address of the switched mode power supply (100, 200, 300) using a first technique if a value of the external resistor (Rx) is greater than a threshold value; set the communication address of the switched mode power supply (100, 200, 300) using a second technique if the value of the external resistor (Rx) is less than the threshold value; determine the value of the external resistor (Rx) a first time with the first technique; compare the first determined value of the external resistor (Rx) with the threshold value; and if the first determined value of the external resistor (Rx) is less than the threshold value, determine the value of the external resistor (Rx) a second time using the second technique and set the communication address based on the second determined value of the external resistor (Rx); wherein the control circuit (110, 210, 310) does not determine the value of the external resistor (Rx) the second time using the second technique if the first determined value of the external resistor (Rx) is greater than the threshold value.