What is 'shielded' vs 'drain' in shielded cables?

What is 'shielded' vs 'drain' in shielded cables?

• A. Shield is for appearance; drain wire carries current.
• B. Shielded uses metal construction solely for mechanical protection.
• C. Shield provides EMI protection; drain wire is tied to ground to drain noise.
• D. Shield protects against moisture only.

Answer: (C)

Shielded means there is a metal layer around the inner conductors that blocks external electromagnetic interference from affecting the signal and helps keep the signal from radiating out. The drain wire is a separate conductor included with the cable that is bonded to that shield and tied to ground to provide a low-impedance path for noise to flow away. It’s not part of the signal path itself; its job is to drain interference into ground and keep the shield effective. The shield itself can be foil, braided, or a combination, and the drain wire is typically a bare copper conductor used during installation to establish a solid equipment ground.

Shielded means there is a metal layer around the inner conductors that blocks external electromagnetic interference from affecting the signal and helps keep the signal from radiating out. The drain wire is a separate conductor included with the cable that is bonded to that shield and tied to ground to provide a low-impedance path for noise to flow away. It’s not part of the signal path itself; its job is to drain interference into ground and keep the shield effective. The shield itself can be foil, braided, or a combination, and the drain wire is typically a bare copper conductor used during installation to establish a solid equipment ground.