*Question E8B05:
What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 5 kHz if the highest modulation frequency is 3 kHz?*  

*Correct Answer is  D: 1.67*  

### AI Response: (may contain errors)  

To find the deviation ratio of an FM phone signal, we use the formula:

$$
\text{Deviation Ratio} = \frac{\Delta f}{f_m}
$$

where:
- $\Delta f$ = maximum frequency swing (deviation)
- $f_m$ = highest modulation frequency

In this case:
- The maximum frequency swing is $\pm 5 \text{ kHz}$, so $\Delta f = 5 \text{ kHz}$.
- The highest modulation frequency is $3 \text{ kHz}$, so $f_m = 3 \text{ kHz}$.

Now, we can calculate the deviation ratio:

$$
\text{Deviation Ratio} = \frac{5 \text{ kHz}}{3 \text{ kHz}} \approx 1.67
$$

### Explanation of the Correct Answer:
- The correct answer is **1.67** because we calculated the deviation ratio using the given values, and it matches the result of our formula.

### Explanation of Incorrect Choices:
- **Choice A: 6**
  - This value would imply a much larger deviation relative to the modulation frequency, which is not supported by the given data.
  
- **Choice B: 0.167**
  - This value suggests that the deviation is much smaller than the modulation frequency, which is incorrect based on our calculation.
  
- **Choice C: 0.6**
  - This value also indicates a smaller deviation relative to the modulation frequency, which does not align with the calculated ratio of 1.67.

### Summary:
- The deviation ratio is a measure of how much the frequency of the carrier wave varies in response to the modulation signal. A ratio of 1.67 indicates that the frequency deviation is 1.67 times the highest modulation frequency, which is typical for FM signals.