Sentry alerts that work with no internet and no app

Sentry posts needed a way to raise an alert instantly, and the command centre needed to know that every post was manned and where each sentry was. Phones and apps were not an option on duty, and the system could not depend on internet connectivity.

Each sentry carries a small unit with a single power button. Press patterns are configured centrally: for example one press, two presses or a long series, each meaning a different alert. Units check in on a regular schedule, so a missed check-in is itself an alert. Alerts, check-ins and each sentry's location travel over the cellular network to the central command and control centre at HQ TASA, where duty staff see every post on one screen.