*Question T2A11:
What term describes an amateur station that is transmitting and receiving on the same frequency?*  

*Correct Answer is  C: Simplex*  

### AI Response: (may contain errors)  

The correct answer to the question is **Simplex**.

### Explanation of the Correct Answer:
- **Simplex** refers to a communication mode where a station can either transmit or receive at any given time, but not both simultaneously. In amateur radio, this means that when one station is transmitting, the other must wait until the transmission is complete before responding. This is commonly used in many radio communications, including most amateur radio operations.

### Why the Other Choices are Incorrect:
- **A: Full duplex**  
  - Full duplex allows for simultaneous transmission and reception on the same frequency. This is not applicable in this context, as simplex does not permit both actions at the same time.

- **B: Diplex**  
  - Diplexing involves using two different frequencies for transmitting and receiving, typically through a diplexer. This is not relevant to the definition of a station operating on the same frequency.

- **D: Multiplex**  
  - Multiplexing refers to the technique of combining multiple signals over a single communication channel. This does not describe the operation of a station transmitting and receiving on the same frequency.

### Summary:
- **Simplex**: One station transmits while the other listens, but not at the same time.
- **Full duplex**: Both stations can transmit and receive simultaneously.
- **Diplex**: Uses different frequencies for transmit and receive.
- **Multiplex**: Combines multiple signals into one channel.

Understanding these terms is crucial for effective communication in amateur radio and for passing the Extra Class exam.