Abstract: A launching barrel/oscillator module simulation unit is provided for simulating a plurality of launcher barrels and associated oscillator module of an aerial (infra-red or chaff) decoy arrangement. The unit is adapted for connection to a launcher control module (LCM) of the arrangement which sends command information over a data link (DB) for the operation of the launcher/barrel oscillator module (LCM) in accordance with specific decoy requirements. The unit is effective for sending status information back to the launcher control module (LCM) over the data link (DB) and basically comprises (i) a plurality of switches in respect of each simulated barrel and operable in dependence upon the condition (e.g.