A communication system of a battery pack, wherein the communication system comprises a transmitter (no) configured to transmit a first communication signal from the battery pack to an external device and a receiver configured to receive a second communication signal from the external device, wherein the transmitter comprises: a first transistor (TR1) configured to perform a switching operation in response to the first communication signal, which is output from a battery management system (BMS) of the battery pack; a second transistor (TR2) configured to perform a switching operation in response to the switching operation of the first transistor, wherein the first communication signal is transmitted through the first and second transistors to the external device when the first and second transistors are turned on; and a first diode (D1) configured to transmit the first communication signal to the external device when the first and second transistors are turned off, and the receiver comprises: a third transistor (TR3) configured to perform a switching operation in response to the second communication signal, which is received from the external device; a fourth transistor (TR4) configured to perform a switching operation in response to the switching operation of the third transistor, wherein the second communication signal is transmitted through the third and fourth transistors to the BMS when the third and fourth transistors are turned on; and a second diode (D2) configured to transmit the second communication signal to the BMS when the third and fourth transistors are turned off. a first transistor (TR1) configured to perform a switching operation in response to the first communication signal, which is output from a battery management system (BMS) of the battery pack; a second transistor (TR2) configured to perform a switching operation in response to the switching operation of the first transistor, wherein the first communication signal is transmitted through the first and second transistors to the external device when the first and second transistors are turned on; and a first diode (D1) configured to transmit the first communication signal to the external device when the first and second transistors are turned off, and the receiver comprises: a third transistor (TR3) configured to perform a switching operation in response to the second communication signal, which is received from the external device; a fourth transistor (TR4) configured to perform a switching operation in response to the switching operation of the third transistor, wherein the second communication signal is transmitted through the third and fourth transistors to the BMS when the third and fourth transistors are turned on; and a second diode (D2) configured to transmit the second communication signal to the BMS when the third and fourth transistors are turned off. a third transistor (TR3) configured to perform a switching operation in response to the second communication signal, which is received from the external device; a fourth transistor (TR4) configured to perform a switching operation in response to the switching operation of the third transistor, wherein the second communication signal is transmitted through the third and fourth transistors to the BMS when the third and fourth transistors are turned on; and a second diode (D2) configured to transmit the second communication signal to the BMS when the third and fourth transistors are turned off. <EOS>