*Question E8B06:
What is the deviation ratio of an FM phone signal having a maximum frequency swing of plus or minus 7.5 kHz if the highest modulation frequency is 3.5 kHz?*  

*Correct Answer is  A: 2.14*  

### 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 $\pm 7.5 \text{ kHz}$, so $\Delta f = 7.5 \text{ kHz}$.
- The highest modulation frequency is $3.5 \text{ kHz}$.

Now, we can calculate the deviation ratio:

$$
\text{Deviation Ratio} = \frac{7.5 \text{ kHz}}{3.5 \text{ kHz}} \approx 2.14
$$

### Explanation of the Correct Answer:
- The correct answer is **2.14** because it accurately reflects the ratio of the maximum frequency deviation to the highest modulation frequency. This ratio indicates how much the frequency of the carrier wave varies in response to the modulation signal.

### Explanation of Incorrect Choices:
- **A: 2.14** - This is the correct answer.
- **B: 0.214** - This value is incorrect because it represents the inverse of the correct ratio. It would imply that the modulation frequency is much larger than the deviation, which is not the case here.
- **C: 0.47** - This value is also incorrect. It suggests a much smaller deviation ratio, which does not match the calculated value.
- **D: 47** - This is incorrect as it implies an extremely high deviation ratio, which is unrealistic given the values provided.

### Summary:
- The deviation ratio is a crucial parameter in FM communication, indicating how much the carrier frequency deviates from its resting frequency based on the modulation signal. Understanding this concept helps in analyzing FM signals and their bandwidth requirements.