Gents , thank you for your answers and explanations.
The a/c , I have worked on is an ex-SQ (ex-SPB) , thats the reason why Mr Leewan knows about it .
It was the first time that I saw this system , anyway I worked only on the 744 from AF , AC , TG , JL , NH , KE and BR and none of them get it (as far as I can remember...).
Happy to see that even after 20 years experience , I am still discovering new things (from the 60s) ...(who is laughing ?).
Merci.