A primary circuit produces a first on-pulse and a first off-pulse synchronized with a rising edge and a falling edge of an input signal, respectively. A level shift circuit produces a second on-pulse and a second off-pulse formed by shifting the voltage level of the first on-pulse the first off-pulse, respectively. A secondary circuit outputs an output pulse rising and falling in synchronization with the second on-pulse and the second off-pulse, and holds the output when both of the pulses are high. When the reference potential rises, the pulse corresponding to the state of the input signal during the rise of the second potential in the first on-pulse and the first off-pulse is regenerated and one of the second on-pulse and the second off-pulse is thereby made high after the end of the rise of the second reference potential to retransmit the state of the input signal.