I think we had a topic on that earlier if my memory serves me well? How can we help?
The use is down to the User - the A20 has adaptors for all sorts of applications and each one is designed for each Aircraft or Heli type we assume. They all work the same way as far as the Headphones, but the Mics, Leads, Powering Options and Mic Impedances etc differ according to the Audio Interfaces offered by the Aircraft Manufacturer and Audio Panel Designers.
Can you offer any further info so that we may offer a better response at all?