4.3.1 Countermeasures against the CMOS self-oscillation by input open-failure 
Fail-safe measures for the relay drive circuit shown in Figure 4.4 are discussed below. Figure 4.8 illustrates the equivalent circuit of an Inverter IC for consideration the CMOS IC operation [39], where the input signal is operated at a low level, the output is pulled to through the PMOS device (and is turned OFF). When the input signal is operated at a high level, the output is pulled to ground through the NMOS device (and is turned OFF).