Propagation of digital signals under the influence of noise, the Noise Margin High is [blank_start]V(OH)[blank_end] minus [blank_start]V(IH)[blank_end] and, the Noise Margin Low is [blank_start]V(IL)[blank_end] minus [blank_start]V(OL)[blank_end].
For CMOS Inverter Circuit, when Input is 1, the Output is 0 and the [blank_start]PUN[blank_end] is off; when Input is 0, the Output is 1 and the [blank_start]PDN[blank_end] is off.