Height Code Tables for Use with Air Traffic Control Radar Beacon System

摘要

The Seventh Communications Division of the International Civil Aviation Organization (ICAO) has recommended the adoption of a digital code for automatic height transmission via the AIR TRAFFIC CONTROL RADAR BEACON SYSTEM. Salient features of the code are (1) One-hundredfoot digitizing increments; (2) Range from -1000 feet to +126,750 feet; (3) Compatibility with limited-capability 500-foot incremented code; (4) Unambiguous unit-distance characteristic; (5) Height transmission with respect to a fixed datum of 1013.2 millibars (29.92 inches of mercury). The code, as recommended by ICAO, is tabulated for height increments in increasing numeric order and for the equivalent octal Mode 3/A reply in increasing numeric order. The PULSE POSITIONS column lists the timesequence assignment of the pulse-transmission reply, and the HEIGHT CODE POSITIONS column gives a rearrangement of the code information in significant-digit sequence. Five-hundred-foot increments are extracted from the tables by omitting the C information pulses for the appropriate integer multiple of 500-foot height. (Author)