Definition
A series of radio pulses transmitted in a specific, recognizable pattern of timing and spacing, used by radar and transponder systems to identify, distinguish, or trigger a response from cooperating equipment. In ATC radar, it is the patterned interrogation signal sent from the ground that an aircraft transponder recognizes and replies to.
Plain English
A short burst of radio pulses arranged in a set pattern, like a knock with a particular rhythm. The receiving equipment recognizes the pattern and knows to respond.
Context Anchor
Seen in discussions of ground-based radar, aircraft transponders, and how ATC radar identifies aircraft.
Derivation
Coded means arranged in a deliberate pattern that carries meaning. Pulse means a short burst of energy. Sequence means a set order. Together: short bursts of radio energy sent in a deliberate order so the receiver can recognize them and respond correctly.
Why Pilots Care
Allows ATC to positively identify each aircraft on the radar screen and receive altitude information automatically.
Analogy
It is like flashing a light in a specific pattern instead of speaking words. The individual flashes are simple, but their timing and order carry the message.
Intuition Check
Coded does not mean secret or encrypted here. It means the pattern of short radio bursts is arranged so radar equipment can interpret it.
Example Sentence 1
The ground radar transmits a coded pulse sequence, and the aircraft transponder replies with its assigned squawk and altitude.
Example Sentence 2
Controllers rely on each aircraft returning a distinct coded pulse sequence so they can track multiple targets without confusion.