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Systems

Cross-cutting topics that span multiple instruments — buses, protocols, power distribution, signal types. If a topic is intrinsic to how a class of instruments communicates rather than to any one instrument, it lives here. Each topic folder also holds the generic test methods for that bus or signal type — how to sniff it, drive it, excite it on the bench — alongside the reference for what it is.

What goes here

  • Digital buses — ARINC 429, ARINC 561, ARINC 568, ARINC 615.
  • Analog signal types — synchros, resolvers, AC ratiometric inputs, DC analog.
  • Power — 28 VDC distribution, 115 VAC / 400 Hz, 26 VAC reference, emergency bus topology.
  • Audio — interphone, hot-mic conventions, sidetone.
  • Discretes — open/ground signaling conventions, lamp drivers, weight-on-wheels logic.

Each topic folder typically contains:

  • README.md — what the system is: mechanics, conventions, reference.
  • test-methods.md — how to sniff, drive, or characterize it from the bench (applies to any unit using this signal type).
  • Supporting files (label tables, fixture notes, captures) as needed.

What doesn't go here

Instrument-specific behavior — even if it involves one of these systems — goes in avionics/<unit>/. Use this directory for the general protocol or signal-type reference (and the general test methods), then link to it from individual unit docs.

Index

Add system topics here as they're created.

Suggested starter topics, in rough priority order:

  • arinc-429/ — bus mechanics, label structure, common labels, sniffing/driving methods.
  • synchros/ — 3-wire synchro signals, 26 VAC reference, common excitation schemes, bench excitation methods.
  • 28-vdc/ — typical aircraft DC distribution and protection.
  • 400hz-ac/ — aircraft AC power, why 400 Hz, transformer behavior.