discrete code

discrete code

Any one of the 4096 selectable Mode 3/A four-digit SSR (secondary surveillance radar) codes whose last two digits are not “00” (e.g., discrete codes: 0010, 1201, 2317, 7777; nondiscrete codes: 0100, 1200, 7700). Nondiscrete codes are normally reserved for radar facilities that are not equipped with discrete decoding capability and for other purposes such as emergencies (7700), VFR (visual flight rules), aircraft (1200), etc.