*Question E6C08:
In Figure E6-3, which is the schematic symbol for a NAND gate?*  

*Correct Answer is  B: 2*  

### AI Response: (may contain errors)  

In digital electronics, a NAND gate is a fundamental building block. It is a combination of an AND gate followed by a NOT gate. The output of a NAND gate is true (or high) unless both of its inputs are true (or high).

### Explanation:

1. **Correct Answer: B (2)**
   - The schematic symbol for a NAND gate is similar to an AND gate but with a small circle (representing the NOT operation) at the output. This circle indicates the inversion of the AND gate's output.
   - In Figure E6-3, symbol 2 has this characteristic: it looks like an AND gate with a small circle at the output.

2. **Why the Other Choices are Incorrect:**
   - **Choice A (1):** This is the symbol for an AND gate. It does not have the inversion circle at the output, so it is not a NAND gate.
   - **Choice C (3):** This is the symbol for an OR gate. It has a different shape and does not include the inversion circle.
   - **Choice D (4):** This is the symbol for a NOR gate. It looks like an OR gate with an inversion circle, which is not the same as a NAND gate.

### Useful Rule of Thumb:

- **NAND Gate Logic:**
  - The output $Q$ of a NAND gate with inputs $A$ and $B$ is given by:
  $$ Q = \overline{A \cdot B} $$
  - This means the output is the negation (NOT) of the AND operation on inputs $A$ and $B$.

Understanding these symbols and their functions is crucial for interpreting digital circuit diagrams and for the FCC exam.