Figure 4.22 shows the waveform diagram of the fault situation in the power input signal. By the fault in an input part, the power signal is not provided to relay driver circuit, is cleared when the input is in 0V. This means that without a drive signal to M1 and M2 in this state. Similarly, in case of the control part has a failure, which makes clearing the control signal of the driver device. Even if an input signal is not lower than 5V, the relay driver is not available.