Aerodec inquired about a solution for the requirement to provide an additional aural airspeed warning, for use in the Boeing 727 aircraft that were being modified to a dispersant role for tackling oil spills worldwide. The aircraft were, at the time, fitted with a dual IS&S Air-data system. Because the aircraft were fitted with a dispersant spray boom at the aft end, they would be subject to a speed limit of around 270kts. In the absence of any easily configurable differential pressure switch, Aerodac asked if an AIS unit could be used to convert the CAS output from No. 2 Synchro to a switched DC ground at the prescribed airspeed or tie into an output. Shadin proposed solving the issue with the AIS-360 ARINC 429 Airspeed to Discrete Adapter. The unit was designed to receive ARINC 429 label for airspeed and output a 28 VDC discrete at 270 knots.