*Question T4A12:
What is an electronic keyer?*  

*Correct Answer is  C: A device that assists in manual sending of Morse code*  

### AI Response: (may contain errors)  

An electronic keyer is a device that assists in the manual sending of Morse code. It allows operators to send Morse code more efficiently by generating the necessary on-off keying signals based on the operator's input.

### Explanation of the Correct Answer:
- **Correct Answer: C** - An electronic keyer helps operators send Morse code by converting the operator's manual input (usually via a paddle) into a series of dots and dashes. This makes it easier to send Morse code accurately and at higher speeds than manual keying alone.

### Explanation of Incorrect Answers:
- **A: A device for switching antennas from transmit to receive**  
  This describes an antenna switch or relay, not an electronic keyer. An electronic keyer does not switch antennas; it focuses on generating Morse code signals.

- **B: A device for voice activated switching from receive to transmit**  
  This refers to a voice-operated switch (VOX), which is used in voice communication, not Morse code. An electronic keyer does not operate based on voice activation.

- **D: An interlock to prevent unauthorized use of a radio**  
  This describes a security feature or lockout mechanism, which is unrelated to the function of an electronic keyer. An electronic keyer is specifically designed for Morse code transmission.

### Summary:
- An electronic keyer is essential for efficient Morse code operation, allowing for faster and more accurate sending.
- Remember that it is distinct from devices that manage antenna switching, voice activation, or security functions. 

This understanding will help you recognize the role of an electronic keyer in amateur radio operations.