Mode

The letter or number assigned to a specific pulse spacing of radio signals transmitted or received by ground interrogator or airborne transponder components of the Air Traffic Control Radar Beacon System (ATCRBS). Mode A (military Mode 3) and Mode C (altitude reporting) are used in air traffic control.

Source: FAA Pilot/Controller Glossary (definition from the 2023 edition; current: Change 1 of 7 August 2025).

Reference: AIM.

See also

Related terms

Glossary last updated 2026-10-28.

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A
B
C
D
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F
G
H
I
J
K
L
M
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P
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U
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X
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