The purpose of a detector at the receiving end is

Options

A. to amplify signal
B. to reduce its frequency level
C. to modulate signal
D. to demodulate signal

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of the Detector:**
The detector is a crucial component in a communication system, particularly at the receiving end. Its primary function is to process the received signals.

2. **Modulation and Demodulation:**
In communication systems, modulation is the process where the original low-frequency signal is superimposed onto a high-frequency carrier wave. This is done by the transmitter. Conversely, demodulation is the process of extracting the original signal from the modulated carrier wave at the receiver.

3. **Function of the Detector:**
The detector's main role is to demodulate the incoming signal. This means it removes the carrier wave that was added during modulation and retrieves the original low-frequency signal that was transmitted.

4. **Clarifying Misconceptions:**
- The detector does not amplify the signal; amplification is typically handled by other components in the receiver.
- The detector does not reduce the frequency level; it simply extracts the original signal.
- The detector does not modulate the signal; modulation is performed by the transmitter.

5. **Conclusion:**
Therefore, the purpose of the detector at the receiving end is to demodulate the signal, allowing the receiver to recover the original information that was sent.

**Final Answer:**
The purpose of a detector at the receiving end is to demodulate the signal.

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