asterisk users - Feb 2008 - SPA3000 + asterisk +call waiting

Hi, all

A quick question.
I have SPA3000 and trying to get call waiting to work. I do receive
call waiting tone, however hook flash does not seem to work. I think,
I set up SPA3000 correctly.

Basically, doing HF 2 (switching calls in Australia) does not do anything.

Is there any examples on how to setup hook flash operation in Asterisk?

Thanks,
Rudolf