The intrinsically safe pre-start alarm controller type APSA2 is part of the Austdac Pre-Start Alarm and Communications System type PSACS1 that provides two-way voice communications and pre-start alarm facilities along distributed plant such as conveyor belts, crushers, stacker-reclaimers and longwalls. The pre-start alarm controller is responsible for initiating pre-start alarms, confirming pre-start alarms, tone generation and control of voice communications along the belt as well as to the surface or control room.