hp 3311 A function generator GPIB

Hi, I've a Hp 3311 A function generator and I'd like to control it by GPIB. I'd tested with the example in labview "GPIB.vi" but when i send it a command, pej "APPLIN 1.0E+3, 3.0, -2.5" it doesn't work (It makes only a sound "Bip" ).

Does anyone knows why the function generator doesn't generate the signal?

Note: When i send it the command IND?, the instrument returns the name "Hp 3311A", but when i send another command it doesn't work.

Thanks. Regards, peliasrojo.