Red Seal Electrician Practice
Signalling and communicationQuestion 44 of 1506

In frequency shift keying (FSK), how are the binary states 1 and 0 shown?

  1. By two different voltage levels of a square wave
  2. By sine waves of two different frequencies
  3. By the presence or absence of a carrier only
  4. By the colour of light in a fibre
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Correct answer: By sine waves of two different frequencies

FSK is frequency modulation applied to digital data.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 14.4: Electrical Signal Types

Practice signalling and communication

Questions last reviewed: 18 October 2026