*Question E7E03:
What is a frequency discriminator?*  

*Correct Answer is  D: A circuit for detecting FM signals*  

### AI Response: (may contain errors)  

A frequency discriminator is a circuit used to detect frequency-modulated (FM) signals by converting frequency variations into amplitude variations. 

### Correct Answer: 
**D: A circuit for detecting FM signals**

- **Explanation**: 
  - A frequency discriminator works by taking an FM signal and producing an output that is proportional to the frequency deviation of the input signal. This allows the circuit to effectively demodulate the FM signal, making it suitable for audio or data recovery.

### Why the Other Choices are Incorrect:

- **A: An FM generator circuit**  
  - This is incorrect because an FM generator creates frequency-modulated signals rather than detecting them. It modulates a carrier frequency based on an input signal.

- **B: A circuit for filtering closely adjacent signals**  
  - This is incorrect because filtering circuits are designed to separate signals based on frequency, not to detect or demodulate them. A frequency discriminator specifically focuses on detecting frequency variations in an FM signal.

- **C: An automatic band-switching circuit**  
  - This is incorrect because an automatic band-switching circuit is used to change frequency bands in a transceiver based on certain conditions, not for detecting FM signals.

### Summary:
- A frequency discriminator is essential for demodulating FM signals, converting frequency changes into corresponding amplitude changes for further processing. Understanding this concept is crucial for the Extra Class exam, as it relates to signal processing and communication systems.