What does the preamble in secure communications consist of?

• A. A single audible tone
• B. A sequence of numbers
• C. A verbal password
• D. A silent signal

Answer: (A)

The preamble’s job is to establish synchronization and readiness at the start of a secure transmission. A single audible tone provides a quick, unmistakable cue that the receiver can lock onto right away, setting the timing and carrier reference before any encrypted data begins. This makes detection and synchronization robust with minimal processing.

A sequence of numbers would look like data, not a simple synchronization cue, and adds complexity for detection. A verbal password would introduce human-related variability and security concerns, and would require additional handling. A silent signal wouldn’t alert the receiver to the start of transmission or provide a clear timing reference.