Which of the following statements about shielded cables is correct?

• A. They are never required in aircraft wiring
• B. They are optional, only for high-end systems
• C. They minimize EMI and crosstalk by shielding signals from external interference
• D. They replace the need for proper routing

Answer: (C)

Shielded cables use a conductive layer wrapped around the inner conductors and tied to ground. That shield acts like a shielded barrier: it absorbs and redirects electromagnetic interference away from the signal-carrying conductors and helps keep signals from leaking into neighboring cables, which reduces crosstalk. In an aircraft, where wires run near power cables, motors, and RF equipment, this shielding is essential to maintain signal integrity for sensitive avionics and communications.

The idea that shielding is never required isn’t accurate, since EMI and crosstalk can seriously degrade performance in many installations. It isn’t only for high-end systems either; shielding is a common practice in avionics where noise is a real concern. And shielding doesn’t replace proper routing—careful routing and separation of cables are still important to minimize coupling and interference. Grounding the shield appropriately is also important; improper grounding can create ground loops or fail to provide effective protection.