What is the purpose of using shielded cable in control and signaling applications?

• A. To increase voltage rating
• B. To reduce EMI/RFI interference and protect signal integrity
• C. To reduce conductor size
• D. To improve mechanical strength

Answer: (B)

Shielded cable is used to keep signals clean in control and signaling by blocking external electrical noise. The metal shield surrounds the conductors and, when grounded, shunts unwanted EMI/RFI to ground, reducing interference picked up by the conductors and preventing noise from corrupting the signal. This helps preserve signal integrity for low-level control signals and also reduces cross-talk between nearby cables. It’s not about increasing voltage rating, nor about reducing conductor size, and while shielding can offer some mechanical protection, that isn’t its primary purpose.