In a telemetry channel, overhead refers to which of the following?

• A. The payload data itself
• B. Framing, headers, CRCs, and other non-payload bits
• C. Encryption keys only
• D. The modulation scheme used

Answer: (B)

Overhead is the extra information that rides alongside the actual data to make transmission reliable and usable. In a telemetry channel, this includes framing that marks where each piece of data starts and ends, headers that carry addressing and sequencing information, and error-detection codes like CRCs that let the receiver verify integrity. These bits don’t carry the actual telemetry measurements or commands themselves, but they are essential for organizing, routing, and checking data as it moves through the system.

The actual payload data is the true telemetry content—the measurements or messages you care about. Encryption keys are related to security and key management, not the routine overhead that supports data framing and error checking. The modulation scheme is a method for turning digital bits into a radio signal at the physical layer; while it affects performance, it’s not the set of extra control information that defines overhead.