Which cable assemblies require the drain wire and screen foil to be bonded at every connection?

• A. Screened twisted pair cable assemblies
• B. Unshielded twisted pair cable assemblies
• C. Coaxial cables
• D. Fiber optic assemblies

Answer: (A)

The key idea is shield continuity. In screened twisted pair cables, the conductors are wrapped in a foil shield (and often have a drain wire that grounds the shield). To keep the shield effective along the entire run, the drain wire and the shield must be bonded at every connection. This grounding at each junction ensures a continuous low-impedance shield path, which minimizes EMI, crosstalk, and charge buildup and provides a consistent ground reference for the connected equipment.

Unshielded twisted pair has no shield to bond, so this isn’t required. Coaxial cables do have shielding, but bonding practices focus on grounding the shield at the enclosure or endpoints rather than at every intermediate connector. Fiber optic assemblies have no metallic shield at all, so there’s nothing to bond.