*Question T4B02:
Which of the following can be used to enter a transceiver’s operating frequency?*  

*Correct Answer is  A: The keypad or VFO knob*  

### AI Response: (may contain errors)  

The correct answer to the question is **A: The keypad or VFO knob**. Here's a breakdown of why this is the case and why the other options are incorrect:

1. **Why the correct answer is correct:**
   - The **keypad** allows you to directly input the desired frequency numerically.
   - The **VFO (Variable Frequency Oscillator) knob** lets you manually adjust the frequency by turning the knob, which changes the operating frequency of the transceiver.
   - Both methods are standard ways to set the operating frequency on most transceivers.

2. **Why the other choices are incorrect:**
   - **B: The CTCSS or DTMF encoder**: 
     - CTCSS (Continuous Tone-Coded Squelch System) is used for squelching and does not set the operating frequency. 
     - DTMF (Dual-Tone Multi-Frequency) is used for signaling and control, not for frequency selection.
   - **C: The Automatic Frequency Control (AFC)**: 
     - AFC is a feature that automatically adjusts the receiver's frequency to stay locked on a signal. It does not allow the operator to set the frequency manually.
   - **D: All these choices are correct**: 
     - Since options B and C do not allow for frequency entry, this choice is incorrect.

3. **Useful rules of thumb:**
   - Always check your transceiver's manual for specific methods of frequency entry, as different models may have unique features.
   - Remember that the VFO knob is often used for fine-tuning frequencies, while the keypad is best for entering specific frequencies directly.

In summary, the keypad and VFO knob are the primary means to enter a transceiver's operating frequency, while the other options serve different functions.