The message signal is usually of:

Options

A. audio frequency range
B. radio frequency range
C. audio or radio frequency range
D. mixture of both

Answer

To solve the question regarding the frequency range of the message signal, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Message Signal**:
- A message signal is a signal that contains information or a message that needs to be transmitted. This can include audio signals, video signals, or any other form of data.

2. **Frequency Range of Message Signals**:
- The frequency range of the message signal is typically lower compared to other types of signals used in communication systems.

3. **Comparison of Frequency Ranges**:
- The audio frequency range is defined as 20 Hz to 20 kHz (20,000 Hz). This is the range that human ears can typically hear.
- In contrast, radio frequency ranges can go much higher, from about 30 kHz to several GHz (gigahertz).

4. **Identifying the Correct Option**:
- Given the options, we need to identify which frequency range corresponds to the message signal.
- Since the audio frequency range (20 Hz to 20 kHz) is the range that is commonly used for message signals, we can conclude that this is the correct answer.

5. **Conclusion**:
- Therefore, the message signal is usually of audio frequency range, which is between 20 Hz and 20 kHz.

### Final Answer:
The message signal is usually of **audio frequency**.

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