Labels Cannot Override Wires - Electronic Circuits IV: Digital Logic Signals and Switch Networks Step by Step

A compact table is useful only because its cells are regenerated from the switch topology. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A wrong NAND label cannot override wires

The NAND table is generated from the same series pull-down topology used in the diagram.

\begin{array}{ccc} A&B&Y\\0&0&1\\0&1&1\\1&0&1\\1&1&0\end{array}

A NOR table is a different topology audit

The NOR table is generated from parallel pull-down branches. The lesson never copies NAND cells into NOR by hand.

\begin{array}{ccc} A&B&Y\\0&0&1\\0&1&0\\1&0&0\\1&1&0\end{array}

Different wires give different accepted tables

The compact tables are accepted because each output cell is recomputed from the corresponding topology. The names NAND and NOR are not enough; the wire graph decides which rows are LOW.

\text{series pull-down} \ne \text{parallel pull-down}