Authentication prevents impersonation on the net. Challenge: one word. Response: one word. The duress code is a specific response word that tells the net control the operator is under duress — the net acknowledges normally but initiates the duress protocol. Document current pairs, alternates, and the rotation schedule. Authentication codes should rotate on the same schedule as your BREACH POINT challenge and response pairs — ideally weekly in an elevated threat environment.

Brevity codes accomplish two things: they reduce transmission time (critical when every second on air is a location indicator) and they obscure meaning from casual monitoring. Build a library of 10–20 codes covering the most common operational messages: all clear, activate, abort, injured, at location, moving to, compromised, request assistance. Keep them short and unambiguous. Every group member must know them cold — these are used under stress.

A net schedule creates accountability and ensures regular communication contact between group members and MAG partners. Document: check-in time (local and Zulu), frequency and mode, check-in format (callsign + status code), and missed contact procedure — what to do if a station misses check-in, how long to wait, and when a missed contact triggers a welfare check. Integrate with COMMS MATRIX net schedules.

The signal card is what SIGNAL BOOK exists to produce. Everything that belongs on the card should fit on a single 3x5 index card, front and back, in legible print. This means abbreviating ruthlessly — frequency numbers, single-letter mode codes, two-word brevity codes. Every group member carries this card at all times. It should be laminated. It should be destroyed if capture is imminent. Generate the card here and print from the Outputs panel.