Practice question

Under ICAO SSR standards, what is the difference between Mode C and Mode S transponder operations?

  1. Mode C transmits pressure altitude in 100-foot increments; Mode S transmits altitude along with a unique 24-bit aircraft address and data link capabilities.
  2. Mode C transmits a 4-digit octal identification code; Mode S transmits only pressure altitude.
  3. Mode C operates on VHF frequencies; Mode S operates on UHF frequencies.
  4. Mode C is a passive skin reflection system; Mode S is an active transponder system.

Answer: A — Mode C transmits pressure altitude in 100-foot increments; Mode S transmits altitude along with a unique 24-bit aircraft address and data link capabilities.

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