*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 determine the deviation ratio of an FM phone signal, we use the formula:

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

where:
- $\Delta f$ is the maximum frequency deviation (in kHz)
- $f_m$ is the highest modulation frequency (in kHz)

For this question:
- The maximum frequency deviation, $\Delta f$, is 7.5 kHz.
- The highest modulation frequency, $f_m$, is 3.5 kHz.

Plug these values into the formula:

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

### Explanation of Choices:

- **A: 2.14**  
  This is the correct answer because it accurately represents the ratio of the maximum frequency deviation to the highest modulation frequency.

- **B: 0.214**  
  This choice is incorrect because it represents a much smaller ratio, which would imply a much smaller frequency deviation relative to the modulation frequency.

- **C: 0.47**  
  This choice is incorrect because it does not match the calculated deviation ratio. It suggests a smaller deviation than what is given.

- **D: 47**  
  This choice is incorrect because it represents an excessively large ratio, which would imply a much larger frequency deviation than what is provided.

Understanding the deviation ratio is important for characterizing the bandwidth and performance of FM signals. The correct calculation ensures proper signal design and compliance with regulations.