British military scientists found a way of exploiting this by building their own IFF transmitter called '' Perfectos '' , which were designed to trigger a response from any FuG 25a system in the vicinity .
British military scientists found a way of exploiting this system to the allies ' advantage . 
 They designed and built their own IFF transmitter called '' Perfectos '' , which was designed to trigger a response from any FuG 25a system in the vicinity .