The duplicated PA/GA package is arranged such that there is no possibility of common mode failure and the design obviates cross transference of possible fault conditions from one sub-system to the remaining working sub-system. Each compartment is fitted with loudspeakers assigned separately to A and B PA/GA sub-systems. In areas where ambient noise exceeds 84 dBA the A and B flashing beacons should be fitted. The two sub-systems are strictly segregated with central panels remotely located from each other.