A communication device includes a first JK flip-flop (FF) outputting a first output signal in response to a first input signal at a J-input and a reversed signal of the first input signal at a K-input, and a second JK FF outputting a second output signal in response to a second input signal at a J-input and a reversed signal of the second input signal at a K-input. A clock input to a NAND gate (12) is replaced by a reversed signal of a Q-output of the second JK FF. A clock input to a NAND gate (13) is replaced by the reversed signal of the second input signal. A clock input to a NAND gate (22) is replaced by a reversed signal of a Q-output of the first JK FF. A clock input to a NAND gate (23) is replaced by the reversed signal of the first input signal.