*Question G8C12:
Which type of code is used for sending characters in a PSK31 signal?*  

*Correct Answer is  A: Varicode*  

### AI Response: (may contain errors)  

In PSK31 (Phase Shift Keying at 31.25 baud), the type of code used for sending characters is Varicode.

### Explanation of the Correct Answer:
- **Varicode** is a variable-length coding scheme specifically designed for use in digital modes like PSK31. It assigns shorter codes to more frequently used characters, which helps to optimize bandwidth and improve efficiency in data transmission. This is particularly useful in low-bandwidth applications like PSK31.

### Why the Other Choices are Incorrect:
- **B: Viterbi**  
  - Viterbi is an algorithm used for decoding convolutional codes, not a coding scheme itself. It is often used in digital communications for error correction but does not pertain to the character encoding in PSK31.

- **C: Volumetric**  
  - Volumetric is not a recognized coding scheme in the context of digital communications or PSK31. This term is more related to measurements of volume and does not apply here.

- **D: Binary**  
  - While binary encoding is fundamental to digital communications, it does not specifically refer to the character encoding used in PSK31. PSK31 uses Varicode, which is more efficient than simple binary encoding for the specific needs of this mode.

### Summary:
- **Correct Answer**: Varicode
- **Incorrect Choices**: Viterbi (decoding algorithm), Volumetric (not applicable), Binary (not specific to PSK31)

Understanding Varicode's role in PSK31 will help you recognize its importance in efficient digital communication.