A telephone facility and an electrical facility are required in a tunnel. To reduce the effects of EMI and eliminate the need for additional shielding of the cables, where would each facility be…

Question

Options

• AOn opposite sides of the tunnel
• BOn the same sides of the tunnel
• CTogether on the same pathway for easy access and maintenance
• DOne on the top part and one on the bottom part of the same side of the tunnel
• EOn the exterior of the tunnel

• A
  81% (13)
• C
  13% (2)
• D
  6% (1)

Explanation

Placing telephone and electrical facilities on opposite sides of the tunnel maximizes the physical separation between the two systems, and since electromagnetic field strength drops off with distance, this spatial separation alone is sufficient to suppress EMI - eliminating the cost and complexity of additional cable shielding. Options B and C are wrong for the same fundamental reason: keeping the cables close together (same side or same pathway) increases inductive and capacitive coupling, which is exactly the source of interference you are trying to avoid. Option D is a tempting near-miss - top vs. bottom on the same side does create some vertical separation, but the cables remain on the same wall where the proximity is still too close for effective EMI rejection. Option E (exterior) is impractical and irrelevant to the internal cable-routing problem.

Memory tip: Think "electrical enemies need space" - in any installation, power and signal cables are adversaries, so you push them to opposite extremes (opposite sides, opposite trenches, opposite conduit banks) to let distance do the shielding work for you.

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