Decodes a 13-bit Mode-S identity (ID) field to a 4-digit octal squawk
string, per ICAO Annex 10 Vol. IV / RTCA DO-260. The field packs each
octal digit across three interleaved pulse bits (e.g. digit A from bits
A4, A2, A1) rather than storing the four digits contiguously.
Decodes a 13-bit Mode-S identity (ID) field to a 4-digit octal squawk string, per ICAO Annex 10 Vol. IV / RTCA DO-260. The field packs each octal digit across three interleaved pulse bits (e.g. digit A from bits A4, A2, A1) rather than storing the four digits contiguously.