A communication system includes a control device and a plurality of electric units configured to be connected to the control device respectively to communicate with each other, and each of the plurality of electric units having a unique identifier. Each of the plurality of electric units comprises a resistor configured to set the corresponding identifiers. The respective resistors of the plurality of electric units are connected to each other in series to form a setting circuit. The control device is configured to determine the corresponding identifiers of the plurality of respective electric units based on magnitudes of respective voltages applied to the plurality of respective resistors in the setting circuit, and to send signals indicating the determined identifiers to the plurality of electric units, respectively.