[asterisk-users] Asterisk call waiting with SIP

Hi

    any body have idea about asterisk call waiting with SIP if we use asterisk1.4.5 & hard phone with extensions.

i need dial plan logic for this which capable to activate & deactivate such feature.

     with ATA & IP phone it is possible but with normal hardphone & SIP in asterisk is it possible to indicate call waiting?

 

plz help me for this

 

Amit