TRICONEX 4329 TRICON 4329 Communication Module TRICONEX 4329 TRICON 4329 Communication Module TRICONEX 4329 TRICON 4329 Communication Module Key switches for system control The main box has a four position key switch that controls all chassis in the system. The Tricon controller, TriStation 1131 software, and control program can read the key switch settings. The switch is set to run normal operations with read-only functionality. The main processor executes a pre loaded control program. Refuse attempts to modify program changes through TriStation 1131, Modbus host, or external host. However, the control program can call the gated access function to enable external host writes during a specified time window. The program is used for program loading and checkout. Allow control of the Tricon system from the TriStation 1131 platform, including downloading all and downloading changes. It also allows external hosts to write program variables.