*Question E4E06:
What type of electrical interference can be caused by computer network equipment?*  

*Correct Answer is  C: The appearance of unstable modulated or unmodulated signals at specific frequencies*  

### AI Response: (may contain errors)  

The correct answer to the question about electrical interference caused by computer network equipment is:

**C: The appearance of unstable modulated or unmodulated signals at specific frequencies.**

### Explanation of the Correct Answer:
- **Computer network equipment**, such as routers and switches, often generates electromagnetic interference (EMI) due to the high-speed digital signals they use. This interference can manifest as unstable signals on the radio spectrum, which may appear as noise or spurious signals at specific frequencies. These signals can disrupt normal operation of nearby radio equipment, leading to poor reception or unwanted noise.

### Why the Other Choices are Incorrect:
- **A: A loud AC hum in the audio output of your station’s receiver**
  - This type of interference is typically caused by power line noise or other AC sources, not specifically by computer network equipment. It is more associated with 60 Hz (or 50 Hz in some countries) hum from electrical systems.

- **B: A clicking noise at intervals of a few seconds**
  - Clicking noises are often related to intermittent connections or switching power supplies, but they are not characteristic of interference from computer network equipment. This type of noise is more likely from devices like relays or mechanical switches.

- **D: A whining-type noise that continually pulses off and on**
  - This description is more indicative of interference from devices like fluorescent lights or other types of switching power supplies, rather than the digital signals from computer network equipment. Such noises are usually not stable and continuous like the interference from network devices.

### Summary:
- Computer network equipment primarily causes interference that appears as unstable signals at specific frequencies, which can disrupt radio communications. Understanding the nature of these interferences helps in identifying and mitigating them effectively.