You also have to make sure the extension or external line to which the extension you're are trying to send call waiting tone to, is "intrudable" at the same or lower priority as the other extensions.
If you are trying to initiate call waiting tone to another extension:
1)Your extension must be capable of sending call waiting tone (and make sure you're using the right feature code.
2)The extension you're trying to send the CAW tone to, must be cabable of receiving CAW tone and be "intrudable" at the same or lower priority as you.
3)The party (either internal or external)to which the extension above is connected must also be "intrudable" for this all to work.
Good luck,
Dave Strang