Two inputs to the NOR gate
With two inputs to a gate (see Fig. 45.21), the truth table is more complicated. There are four ways of connecting high and low voltages to the two inputs. According to the two switch positions, the inputs at A and B can be: both 0, °and I, 1 and 0, or both I.
You can see this in the truth table for the NOR gate shown in Fig. 45.21. If both inputs are high (1), the output is still/ow (0). This is a NOR gate.