I am 100% with llanfairpg on that one.
TCAS: I seem to recall reading a whole thread somewhere on here about what AFIS / ATS / ATC / XYZ people are and aren't allowed to call themselves when answering the telephone.... it seemed very open to how / what you read into the various service titles and guide lines. It may have just been a typo, of course - it's only one letter (ATS / ATC!).
