*Question G4C12:
Why must all metal enclosures of station equipment be grounded?*  

*Correct Answer is  D: It ensures that hazardous voltages cannot appear on the chassis*  

### AI Response: (may contain errors)  

To understand why metal enclosures of station equipment must be grounded, let's look at the purpose of grounding:

1. **Correct Answer: D - It ensures that hazardous voltages cannot appear on the chassis**

   - Grounding metal enclosures is a safety measure. If a fault occurs inside the equipment, such as a wire coming loose and touching the metal case, grounding provides a path for the electrical current to safely dissipate into the earth. This prevents the metal chassis from becoming energized with a hazardous voltage, which could cause electric shock if touched.

2. **Why the other choices are incorrect:**

   - **Choice A: It prevents a blown fuse in the event of an internal short circuit**
     - Grounding does not prevent a fuse from blowing. A fuse is designed to blow when there is an overcurrent, which can happen regardless of whether the equipment is grounded. Grounding is about safety, not about preventing fuses from blowing.

   - **Choice B: It prevents signal overload**
     - Grounding is not related to signal overload. Signal overload is a condition where a receiver is overwhelmed by a strong signal, and grounding the chassis does not affect this.

   - **Choice C: It ensures that the neutral wire is grounded**
     - Grounding the metal enclosure is not about ensuring the neutral wire is grounded. The neutral wire is part of the electrical system's wiring and is typically grounded at the service panel. Grounding the chassis is specifically for safety to prevent shock hazards.

In summary, grounding metal enclosures is a critical safety practice to ensure that any fault conditions do not result in dangerous voltages on the equipment's exterior, protecting users from electric shock.