How to use transfer?

Hello all !

in the dial options I give to possiblity to transfer the call.
But once the called user hits ## and then any digit he gets the message :
I am sorry that’s not a valid extension please try again.

And then comes back to the calling user.
Thanks for any feedback on how to get this fixed !

Regards,
Fabianus

( Asterisk 1.4.21.2)

solved, I just discovered that I had to hit one “#” and not two …

Regards,
Fabianus